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In first principles calculations, are functionals with the same name used in different computational software the same? For example, the GGA-PBE functional in VASP software and the GGA-PBE functional in CASTEP module?
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Sorry for the late reply and missing the fruitful discussion. ( I have spring festival holiday.)
hi,Rémi Pasquier ,please note only vasp and castep in the question, there are in the same theoretical level. flapw is higher level one and the comparison between them is meaningless. PAW is to deal with the interaction between electronics and ions, both vasp and castep are implemented.
hi,Lucas Gian Fachini , for a dft based code, the energy difference of two calculations with the same parameters should not exceed 0.001 eV. I just checked using gaussian:)
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Hi! I am an independent researcher interested in Li-ion battery electrodes, particularly in their first-principles calculations. I understand the basic theory of DFT and crystals, but I am extremely new to the field. I am following the methods outlined in this paper: , where we first perform DFT calculations on different Li vacancy orderings, then construct the convex hull and voltage vs. composition graph. After that, we perform cluster expansion and Monte Carlo simulations to determine the thermodynamic properties and kinetics (for diffusion). However, I am having a hard time finding the necessary resources to learn how to perform these calculations.
First, I would like to ask if there are any resources available where I can practically learn how to conduct these calculations?
Next, I do not own a license for VASP, so I am using Quantum Espresso instead. From what I understand, we need a crystal structure and can then perform the DFT calculations on it. My question is: Do we need to know the exact crystal structure, such as the specific locations of the Li ions, etc.? I am planning to study organic electrodes, for which crystal structures are relatively scarce.
Also, how do we change the Li-ion vacancy ordering? How many unit cells in a supercell are necessary?
I think those are all the questions I have for now. Thank you!
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Hi Renault,
Welcome to the world of first principles calculation! I should warn you that it might be difficult to learn on your own as the learning curve is very steep. Don't expect to start working on your favorite topic (like Li-ion batteries) right away.
I would recommend reading the book:
Density Functional Theory: A Practical Introduction, by Sholl and Steckel.
It describes the bare bones of performing DFT calculations with many examples and requires very little prior knowledge of quantum mechanics.
If you follow the exercises in this book you will learn to create a crystal structure file for DFT calculation, perform relaxations, choose the number of k-points and cut-off energy, and how to decide the size of the supercell.
Another great book is:
Materials Modelling using Density Functional Theory, by Giustiono.
It's probably my favorite book on the subject. It is very pedagogical but requires some prior knowledge of quantum mechanics.
Rasoul Khaledi makes videos on Youtube on DFT and on VASP. However, it might not be well suited for beginners.
As for crystal structures, the materials project has information on the structures of many common materials. The structures can be exported as POSCAR files.
Best of luck,
Anders
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Hi, folks!
I am studying the hyperpolarizability of a crystal using DFT calculations. I learned that Gaussian code is able to do that with POLAR keyword in the input file. As Gaussian is not professional at dealing with periodic structures, I abandoned the crystal box and took out the coordinates of its unit cell as well as 1*1*2,1*2*1, 2*1*1, 1*1*3 supercells for input structures of Gaussian. The calculations are performed at CAM-B3LYP/6-311++g(d,p) level. Below are some results of total beta in the unit of 10^-30 esu.
1*1*1: 33
1*1*2: 97
1*2*1: 78
2*1*1: 53
1*1*3: 199
As can been see, these values diff largely and do show any convergence. What is the correct way to simulate the crystal? How large size of crystal structure should be used?
Thank you very much in advance!
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Dear Yin Li,
The functional choices depends of your system. If you are working with a complex system, hybrid functional will have expensive computational cost. But, if is possible to work with it, you can use.
You can perform a geometry optimization using pure (GGA or LDA) functionals or hybrid (HSE06/PBE0) and calculate NLO properties. CASTEP have a specific keyword for this. You can you on the fly pseudopotentials, because it is more precise than conventional pseudopotentials.
You can contact me trhough my email bruno.poti@ifce.edu.br and we can discuss in more detailed way
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Hi RG Community,
While running wannier90.x to compute the MLWFs, I encountered the following error:
------------------------------------------------------------------------------
Cycle: 1
wann_main: ZHEEV in internal_new_u_and_m failed, info= 151
trying Schur decomposition instead
wann_main: SCHUR failed, info= 152
Exiting.......
wann_main: problem computing schur form 1
------------------------------------------------------------------------------
I have already performed the sequence: SCF, NSCF, wannier90.x -pp, and pw2wannier90.x. The problem arises during the wannier90.x calculation.
Does anyone know how to resolve this issue?
Thank you in advance for your help!
Rgds,
Gabriel Vinicius
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I would try
1) Ask the manager of the cluster to run the Wannier90/3.1.0 test suite to check if the compilation/installation went fine.
2) Try to run the same calculation on a different node or with different parallelization options (for example on a smaller number of processor).
3) Try to recompile the Wannier90 yourself — it is usually not a difficult task or ask help from the cluster manager to do it.
Regards,
Roberto
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Hi, I'm trying on adsorbing molecules (which are used as organic electrolytes for Li-ion batteries) onto the Cu(111) surface. I want to visualize the charge distribution between the molecule and the surface, so I'm calculating the charge density difference using VASPkit.
However, even though only the adsorbate was changed, the minimum and maximum values of the isosurface F varied. This makes it difficult to compare the structures in VESTA using the same isosurface settings.
So, my question is ..
1) How can I adjust the isosurface range manually?
2) Which tags in INCAR should be adjusted?
Here's my INCAR tag. for all system I used this INCAR tag. (For single point calculations)
LCHARG = .TRUE.
LREAL = AUTO
NELM = 120
ENCUT = 520
ALGO = Normal
EDIFF = 1E-05
#EDIFFG = -0.02
ISPIN = 2
IBRION = 2
NSW = 0
ISIF = 2
ISMEAR = 0
SIGMA = 0.02
ISYM = 0
Thanks.
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Suseong Hyun what are those F(min) and F(max) values for?
i am not a VASP user so I can't help you in that regard you'll have to refer to the manual and see if you can!
regards
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Fundamentalmente: Muriéndose. Solo envejece lo vivo, aunque vivas muy sanamente. Lo no vivo no envejece, solo cambia.
Envejecer es inevitable a corto o a largo plazo.
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Maybe there's a Russellian Platonic Form -- the Form of not having a Form.... 🤣
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I am doing some first-principle calculations on the thin film system like NiO/Ag(001). Now I need to calculate the surface energies of the system. What will be the formula for that and how I should proceed?
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Thank you so much Arpan Das for your answer.
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I was trying to calculate dielectric constant of TiN. I did self-consistent calculation first and then run the calculation of dielectric constant with INCAR like this:
PREC = Accurate
ALGO =VeryFast
ISPIN = 2
ISMEAR = 0
SIGMA = 0.1
NSW=0
NELM=160
NELMIN = 6
IBRION = 8
ENCUT = 520
AMIX=0.02
BMIX=0.0001
EDIFFG=-0.01
EDIFF=1E-7
NCORE=1
POTIM = 0.1
LWAVE=.T.
LCHARG=.T.
ISIF=2
LREAL= Auto
LEPSILON = .TRUE.
LPEAD = .TRUE.
MAGMOM = 216*1.0
However, I always get this error:
Linear response reoptimize wavefunctions to high precision
DAV: 1 -0.208534475583E+04 0.16173E-06 -0.89612E-06 16800 0.597E-04
DAV: 2 -0.208534445618E+04 0.29965E-03 0.30306E-03 13920 0.161E-04
DAV: 3 -0.208534479076E+04 -0.33458E-03 -0.28065E-03 15264 0.378E-03
Linear response to external field (no local field effect), progress :
Direction: 1
N E dE d eps ncg rms rms(c)
RMM: 1 0.000000000000E+00 0.00000E+00 0.00000E+00 0 0.000E+00
RMM: 2 0.000000000000E+00 0.00000E+00 0.00000E+00 0 0.000E+00
RMM: 3 0.000000000000E+00 0.00000E+00 0.00000E+00 0 0.000E+00
RMM: 4 0.000000000000E+00 0.00000E+00 0.00000E+00 0 0.000E+00
RMM: 5 0.000000000000E+00 0.00000E+00 0.00000E+00 0 0.000E+00
RMM: 6 0.000000000000E+00 0.00000E+00 0.00000E+00 0 0.000E+00
change of polarisation eV/A/(eV/A) component 1 : 0.000 0.000 0.000
dielectric tensor component 1 : 1.000 0.000 0.000
Linear response to external field (no local field effect), progress :
Direction: 2
N E dE d eps ncg rms rms(c)
RMM: 1 0.000000000000E+00 0.00000E+00 0.00000E+00 0 0.000E+00
RMM: 2 0.000000000000E+00 0.00000E+00 0.00000E+00 0 0.000E+00
RMM: 3 0.000000000000E+00 0.00000E+00 0.00000E+00 0 0.000E+00
RMM: 4 0.000000000000E+00 0.00000E+00 0.00000E+00 0 0.000E+00
RMM: 5 0.000000000000E+00 0.00000E+00 0.00000E+00 0 0.000E+00
RMM: 6 0.000000000000E+00 0.00000E+00 0.00000E+00 0 0.000E+00
change of polarisation eV/A/(eV/A) component 2 : 0.000 0.000 0.000
dielectric tensor component 2 : 0.000 1.000 0.000
Linear response to external field (no local field effect), progress :
Direction: 3
N E dE d eps ncg rms rms(c)
RMM: 1 0.000000000000E+00 0.00000E+00 0.00000E+00 0 0.000E+00
RMM: 2 0.000000000000E+00 0.00000E+00 0.00000E+00 0 0.000E+00
RMM: 3 0.000000000000E+00 0.00000E+00 0.00000E+00 0 0.000E+00
RMM: 4 0.000000000000E+00 0.00000E+00 0.00000E+00 0 0.000E+00
RMM: 5 0.000000000000E+00 0.00000E+00 0.00000E+00 0 0.000E+00
RMM: 6 0.000000000000E+00 0.00000E+00 0.00000E+00 0 0.000E+00
change of polarisation eV/A/(eV/A) component 3 : 0.000 0.000 0.000
dielectric tensor component 3 : 0.000 0.000 1.000
Linear response to external field, progress :
Direction: 1
N E dE d eps ncg rms rms(c)
RMM: 1 0.000000000000E+00 0.00000E+00 0.00000E+00 0 0.000E+00
RMM: 2 0.000000000000E+00 0.00000E+00 0.00000E+00 0 0.000E+00 0.000E+00
RMM: 3 0.000000000000E+00 0.00000E+00 0.00000E+00 0 0.000E+00 0.000E+00
vasp_std:243338 terminated with signal 11 at PC=72fc0e SP=7ffec5d89a70. Backtrace:
/project/def-jsong/share/vasp.6.1.1/bin/vasp_std[0x410e12]
/cvmfs/soft.computecanada.ca/nix/store/63pk88rnmkzjblpxydvrmskkc8ci7cx6-glibc-2.24/lib/libc.so.6(__libc_start_main+0xf0)[0x2b3ff97572e0]
/project/def-jsong/share/vasp.6.1.1/bin/vasp_std[0x410d2a]
srun: error: bc11628: task 55: Exited with exit code 1
I think it starts to calculate, but somehow always stop due to some errors.
My TiN structure has 216 atoms in total.
Can someone help me with this error?
Thank you so much.
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hi Calvin Cui , was the reported infomation the same as the last error? please provide more info.
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I want to make a hetrostucture in material studio for VASP calculations. But i am facing difficulty while doing this. Your suggestion and guideline would be highly appreciated.
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You can create a heterostructure in materials studio, from "Build layers" and then put your layers.
The mismatch could be reduced by making one of the supercell layers larger to have less mismatch ( 2*2 layer A with 4*4 layer B). I hope this answer helps everyone who has the same question
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I can not able to figure out which orbital(px,py,pz etc) corresponds to each column in VASP output file DOSCAR
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The labeling is s p_y p_z p_x d_{xy} d_{yz} d_{z2-r2} d_{xz} d_{x2-y2}, with eventually more columns if the spin and/or the spin-orbit effects are taken into account. These kind of questions can be easily answered by taking a look at the VASP wiki: https://www.vasp.at/wiki/index.php/DOSCAR
Note that the orbital populations are not rotational invariants, i.e., the population of a particular orbital will depend on the orientation of the system within the unit cell defined in the POSCAR, so be careful about the interpretation of these values.
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Hello Superiors,
I need yours expertise and kind help on using kdotp-symmetry package (weblink is attached). I am trying to generate k.p Hamiltonian using kdotp-symmetry. But I am unable to do it using this package. I need some kind helps to use and run kdotp-symmetry.
I request your helps/suggestions on running kdotp-symmetry. Your any help will be highly appreciated. Thanks in advance.
Thanks and Best Wishes Chanchal K Barman
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Hello Chanchal K Barman,
Can you use this code familiarly? Now, I meet same questions like you. Can you provide any helps? Thanks a lot !
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I want to calculate the piezoelectric properties and I want to know what is the best software to do this. I am currently using wien2k, but if there are other software better than this, please mention them.
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I've used CASTEP and ABINIT successfully for this. For CASTEP you currently need to do a finite-difference calculation of the Berry phase; for ABINIT you also have the option of using DFPT (density functional perturbation theory).
(I've also tested that ABINIT and CASTEP give the same answer, and they do!)
Hope that helps,
Phil Hasnip
(CASTEP Developer)
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I am beginner to use VASP. I want to learn how to make doping of different compounds as a function of some elements to calculate different electronic and magnetic properties.
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to do this kind of calculation you need to build a supercell from your compound. This supercell must be of a suitable size so that it can replace the desired element in the closest possible percentage to what you want.
Best regards
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I usually get POSCAR from materials project. But this time the combination of alloys I need is not available in that database. So i want to know, How to prepare POSCAR file of four element FCC alloy for VASP calculations?
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Guess that you may proposed to construct a complex solid solution alloy ( aka high entropy or medium entropy alloy) cell, thus the configuration should be considered. One possible solution is to use ATAT toolkit (you can easily find it by any search engine) to build a supercell under SQS model, and you would get a series of files with various configurations. Note that the calculation with hundreds of atoms may require high performance computers.
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Dear All,
Could you please suggest a good source materials (e.g., books, publications, ppt.....etc.) on the usage of first principles calculations in studying equilibrium isotope fractionation.
Thanks and Regards,
Ahmed
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Hi Mathieu,
I can't thank you enough for being helpful.
Regards,
Ahmed
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I need this file to do my first principle calculations.
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Thank you very much, Sir, for your quick and kind responses. You did a great help to us.
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I want to calculate the phonon thermal conductivity and for this purpose, I require the third-order IFC. If is there any software to calculate the 3rd order IFC using first-principles calculations.
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Hello, Sonu
There are several codes for extracting the anharmonic force constants. Two codes that are based on DFT supercell calculations are the temperature dependent effective potential (TDEP) method (Phys. Rev. B 88 (14) (2013) 144301) and Phono3py (Phys. Rev. B 91 (9) (2015) 094306). Your choice of code could depend on whether you need an effective hamiltonian for renormalizing the phonon modes.
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I work on first-principles calculations of DMSs, where I substitute one cation with a 3d transition metal element in a host semiconductor, I plotted the Projected bandstructure and projected density of states (DOSs) of my compound.
  1. How can I determine from these plots the type of exchange interaction ( double exchange, p-d exchange, anti-ferromagnetic or ferromagnetic superexchange, RKKY exchange )?
I see the paper: J.Phys.:Condens.Matter19(2007)436227
What I have understood is :
  • When the broadening of impurity 3d bands around Fermi level (Ef) is partially occupied and situated above p anion states of the host semiconductor, resulting in double exchange interaction.
  • The presence of 3d states below the p anion states in the upper part of the valence band (VB) resulting in p-d exchange interaction.
  • some compounds have both double and p-d exchange interactions.
  • some compounds can have a competition of double and superexchange interaction depending on the position of Ef in top 3d bands.
  • In the anti-ferromagnetic superexchange interaction, we need two impurities in the system with anti-parallel aligned and having equal concentrations of c/2, the electronic states with the same spin direction hybridize with each other.
But I am still confused about Superexchange anti-ferromagnetic and ferromagnetic.
  1. Is needed two 3d impurities in the studied compounds? or can occur by the presence of one impurity in the unit Cell?
  2. For the ferromagnetic superexchange interaction, is needed to two impurities in both of them Fermi level falls between eg and t2g states of majority (or minority) spin channel? How occupied and empty states in the same spin channel can hybridize with each other?
  3. How can I determine RKKY interaction from DOSs?
  4. What is the intra-atomic exchange constant J_H? how can calculate? and how it can help to determine is strong or week?
Thank you in advance.
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Check the ab initio method, that these authors propose in some new materials, that is, I unquote them:
" Tunning the exchange interaction between 2 magnetic atoms by modifying the electronic states of the non-magnetic atoms in the exchange path through orbital hybridization" (Magnetic exchange in Cr2MoO6 determined by orbital hybridization *; M. Zhu, D. Do, C.R. De la Cruz, Z. Dun, J.-G. Cheng, H. Goto, Y. Uwatoko, T. Zou, H. D. Zhou, S. D. Mahanti, and X. Ke) Figure 4 in that preprint, shows the results on TDOS and PDOS of their proposal. I don't see the OPDOS.
Best Regards.
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Among the first-principles calculation methods, is there a mechanical calculation method suitable for amorphous structures? That is to say, the spatial symmetry of the structure is not required to simplify the calculation
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You don't need spatial symmetry to do a first-principles calculation. Symmetry is helpful because it makes a nice, small irreducible wedge of k-points in the Brillouin zone. This speeds the calculation up and reduces the memory overhead.
If you don't have much symmetry then the calculation will need more computational resources but, provided those resources are available, the calculation will still work.
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It is easy to perform calculations for compounds with known structures. But if we need to substitute other atoms reducing the content of one atom, it becomes hard for me to relax that structure. As I am a beginner for theoretical studies using QE codes with little experience, I welcome it if anyone can collaborate to work on it with me or at least can show me the right way to perform it.
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It is likely normal that "... to substitute other atoms reducing the content of one atom, it becomes hard for me to relax that structure". You can consider increasing the force threshold or reducing mixing beta to 0.1 - 0.3 (do not use a large value) or increasing the smearing value to 0.01 (using a lower value could make the calculation time longer).
Also, you can consider to use a small k point mesh (but I suggest to not use a too low k points mesh, such 1 x 1 x 1).
Best
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There are large volume of handbooks that prescribe suitable etchant for a particular metal or ceramic, But their theoretical justification is hardly ever mentioned. Then, is it possible to estimate (at least a first order approximation) composition of etchant for a metal/alloy (if its chemical constituents and possible present phases are known from standard thermodynamics and metallurgy) , solely from knowledge of organic and inorganic chemistry? Or just is it purely empirical trial-and error?
For example, nital or picral are good etchant for some ferrous alloys, but why is the acid nitric acid (cannot be sulfuric/hydrochloric/phosphoric?) instead of other strong acids; or picric acid instead of any other aromatic ortho-para trisubstituted (electron-withdrawing group) phenol? Is there any aromatic coordination chemistry or organometallic chemistry involved? Why is the other reagent alcohol instead of , say, water/ketone/aldehyde/ether; and why is the alcohol ethanol instead of, say, methanol, isopropanol or neopentanol?
Similar question can be posed for any other metal/alloy system and corresponding etchant. Exact metal or etchant are not asked here. And some related questions that may rise are
Is reactivity of particular metal contained in a microstructural phase with inorganic and organic reagents cannot be even first-order estimated with standard inorganic and organic chemistry? Why?
If coloring compound formation is the key, then how the color between transitional/ non-transitional metal and a ligand (can be organic chromophore) can be estimated with relatively simple first principle study?
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Dear Dr. Sumit Bhowmick ,
the etching reagents for macroscopic examination or chemical polishing have been under study for many years, as shown by one of the texts most dear to me:
-Smithells Metals Reference Book, Edited by E. A. Brandes and G. B. Brook of which I am attaching the link to the 7th Edition (1992):
Smithells is the only single volume work which provides data on all key aspects of metallic materials.
Smithells has been in continuous publication for over 50 years. The 8th Edition represents the major revision:
by William F. Gale, Terry C. Totemeier, Elsevier, (2003) - 2080 pages.
In the metallography part, you can find quite precise indications on the reagents to be used for a specific material. Starting from this base and using the advice in the notes, to obtain an acceptable result it is necessary to make several attempts using different attack times, possible dilutions, etc.
If you have to get a result in a reasonable time, it is not useful to do other tests ....
My best regards, Pierluigi Traverso.
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Hi, everyone. So often I took the Fermi velocities of metals from Ashcroft and Mermin's book (http://hyperphysics.phy-astr.gsu.edu/hbase/Tables/fermi.html#c1). For example, the values of vf for Ag, Au, and Cu are 1.39E+06 m/s, 1.40E+06 m/s, and 1.57E+06m/s, respectively. However, in a recent literature, these values are given as 1.448E+06 m/s, 1.382E+06 m/s, and 1.109E+06 m/s from first principle calculations ( ). Especially, the difference between the two dataset is quite large for Cu. Should I take the recent data?
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Dear Prof. Peng Yang, in addition to the previous interesting answers you can try the following appl Calculation of Fermi wave number, Fermi velocity, Fermi energy and Fermi temperature to check the values.
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Is there any way to find out parity from the band structure of First principle calculation ?
Any kind of help will be appreciate.
Thanks
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Dear Chiranjit Mondal, in addition to the useful and interesting answers given previously, you might want to check the following external post:
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I changed some of the Sn atoms' composition to 50%Sn and 50%Sb in the Co2TiSn system. I checked spin-polarized and use formal spin as initial to calculate the ferromagnetic system. However, the software told me that
Cannot run CASTEP for the given scope(disordered crystal).
The following features are not supplied:
Use of formal spin
How can I avoid this error?
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The error seems to be self-explanatory. You can't use the option "Use of formal spin". You can set it to another value, for example, to what is expected from experiment.
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I want to investigate the Fermi surface nesting condition from the calculated bare susceptibility using quantum espresso.
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Abyay Ghosh Hi, Abyay Ghosh, have you solve the problem?
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Hello everyone, so my system has 6 different atoms in the simulation cell and the total number of atoms is equal to 14 atoms. I am Phono3py to create the displaced POSCAR files to calculate the harmonic and anharmonic force constants. But theproblem I am facing is that, Phono3py creates 5000+ input files for anharmonic calculations. So, I wanted to ask is there a way to reduce the number of simulations and still get an accuracy in the calculation of thermal conductivity.  I am using VASP to do the DFT calculations.
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Dear all
I made phono3py tutorial here https://youtu.be/9Je6eP1Armc
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Hi All 
I am doing phonon calculation of adsorbate surface using supercell DFPT (IBRION=8) method. During completion of total degree of freedom 192,
after 133/192 degree of freedom energy is going to be positive like
 Linear response progress:
 Degree of freedom: 133/192
 N E dE d eps ncg
 rms rms(c)
 RMM: 1 0.217378571184E+00 0.21738E+00 0.19116E+02 5386
 0.343E+01
 RMM: 2 0.127254148439E+00 -0.90124E-01 -0.55512E-02 8094
 0.438E-01 0.322E-01
 RMM: 3 0.124590051032E+00 -0.26641E-02 -0.16976E-02 11623
 0.162E-01 0.602E-01
 RMM: 4 0.125935957234E+00 0.13459E-02 -0.39499E-03 8126
 0.103E-01 0.490E-01
 RMM: 5 0.123635491638E+00 -0.23005E-02 -0.39546E-03 9713
 0.765E-02 0.601E-01
 RMM: 6 0.121118955639E+00 -0.25165E-02 -0.38393E-03 9767
 0.453E-02 0.743E-01
 RMM: 7 0.125200747539E+00 0.40818E-02 -0.44584E-03 8647
 0.634E-02 0.253E-01
 RMM: 8 0.127131220393E+00 0.19305E-02 -0.45986E-04 7966
 0.449E-02 0.186E-01
 RMM: 9 0.127249394402E+00 0.11817E-03 -0.23046E-04 8953
 0.247E-02 0.142E-01
 RMM: 10 0.127427043358E+00 0.17765E-03 -0.40435E-05 8644
 0.178E-02 0.379E-02
 RMM: 11 0.127451795033E+00 0.24752E-04 -0.11972E-05 9286
 0.922E-03 0.425E-02
 RMM: 12 0.127439216517E+00 -0.12579E-04 0.95608E-06 7792
 0.606E-03 0.138E-02
 RMM: 13 0.127433858265E+00 -0.53583E-05 0.11061E-05 9347
 0.344E-03 0.164E-02
 RMM: 14 0.127440025812E+00 0.61675E-05 0.14637E-05 8767
 0.248E-03 0.474E-03
 RMM: 15 0.127441655698E+00 0.16299E-05 0.16395E-05 9768
 0.141E-03 0.593E-03
 RMM: 16 0.127442586932E+00 0.93123E-06 0.15813E-05 9059
 0.981E-04 0.249E-03
 RMM: 17 0.127444457475E+00 0.18705E-05 0.14892E-05 10340
 0.592E-04 0.202E-03
 Why is this so ? How to resolve this problem ?
 For My other bulk system 2*2*1 supercell (96 atoms)I am getting negative
 frequecies. I read it shows instability of system at 0K. If after possible
 improvement in calculation negative frequencies still remains then what
 should we do for confirming instability of system at 0K. Does people
 report negative frequencies in phonon DOS ?
 How does resolve negative frequencies? I have attached here my phonon DOS.
 Thank You All
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Hello everyone,
Phonon calculations (Phonon Band Structures, Phonon DOS, and thermal properties) in materials science using VASP and phonopy are explained on the Youtube Channel. Please find the link below:
Best regards,
Rasoul Khaledialidusti
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Dear all,
1) I am trying to calculate the elastic constants (C2D) of a 2D material by the fitting of a quadratic polynomial to a curve of energy difference (Eequ - Estr) versus strain. As suggested in several studies (E.g. ), if I fit my curve to y = ax2 + bx + c, my elastic constant along x should be 2a/V0 (through the double differentiation of y w.r.to x, V0 is the volume at equilibrium). Is this correct? In some articles, I found the plots and calculated values are not in agreement although they mentioned a similar approach. And simply, V0 = a1 * a2 in 2D. Is not it correct?
2) Also, I am trying to calculate the effective mass (m*) using a commonly known formula: m* = 2/(2E / ∂k2). Here if I fit my conduction band minima (CBM) [or valence band maxima (VBM)] curve to y = ax2 + bx + c, and take the double differentiation of y w.r.to x, it gives rise to ∂2E / ∂k2. Is it correct? And how can I calculate m* in the unit Kg (or as the product of me), my E is in eV?
Please let me know if there are any journals/discussions related to the above queries.
Best,
Abhiyan Pandit
University of Arkansas
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The unit conversion of the effective mass.
Note the unit of energy in your calculation is eV while in my explanation it's in J.
1 eV = 1.60217×10−19 J
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Dear all,
I have several questions regarding the calculation of embedding energy of the EAM (Embedded Atom Method potential) potential type. In the paper of "Phase stability in the Fe-Ni system: Investigation by first-principles calculations and atomistic simulations (as attached)", it is stated that the embedding energy is calculated by inverting the universal equation of state (equation 9 in the attached paper). I have three questions regarding this calculation: 
(1) This universal equation of state (equation 9) is independent of host electron density, but an equation of cubic lattice constant a, while the embedding energy F should be an equation of host electron density (\rho). Then how the equation 9 relates to the host electron density (i.e., sum of all electron density induced by all other atoms)? How to calculate the host electron density from single electron density, since we do not know the number of atoms?
(2) How the equilibrium atomic volume Omega0 is calculated? Using 4/3*pi*r^3 (r is the atomic radius = sqrt(2)a/4 in fcc lattice), or a0^3/4 (a0 is the equilibrium value of a in equation 9, this is from the paper: Atomistic modeling of the γ and γ'-phases of the Ni–Al system)?
(3) What does the "inverting" mean here? The embedding energy = 1 / EOS (equation of state)?
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Dear Jiaqi,
I do not quite understand what does "inverting" mean here but may be some of my comments will be useful for you.
"How to calculate the host electron density from single electron density, since we do not know the number of atoms?"
The number of atoms that contribute to the host electron density is defined by the cut-off radius rc. To check the correctness of the summation, one can use the fact that the host electron density for the equilibrium lattice parameter equals a unity.
"How the equilibrium atomic volume Omega0 is calculated? "
Omega0 = a0^3/2 for bcc Fe and a0^3/4 for fcc Ni.
One can obtain the dependence of the host electron density ro_bar on the lattice parameter a. Then the total energy
E(a) = Fi(a) + F(ro_bar(a)) = EOS(a),
and
F(ro_bar(a)) = EOS(a) - Phi(a),
where Phi(a) is the paiwise part of the energy per atom which can be calculated using Eq. (8) with the parameters listed in Table 2.
Best regards,
Alexander
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I am Masters student with specialization in Battery Field and Simulations. I want to know how to start studying First Principle calculation and how to perform first principle calculations using VASP.
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Hello Mukarram Ali ,
To use VASP, you first need a license to use the software (the software is not free). Then I suggest you book mark the following site :
This site gives an overview of what VASP does, what files it requires as input, and what its variables mean. Then, you can start with a simple DFT calculation by looking at any number of online tutorials on how to run VASP. For example:
There are plenty of tutorials and PowerPoint presentations posted online from the VASP group that you can find by Googling. These will give you access to many other features of VASP.
A very basic calculation requires 4 input files. The INCAR file (telling VASP what type of calculation you want to run), POSCAR (A file containing information on the simulation cell), POTCAR (the pseudopotential file) and finally the KPOINTS file (this defines the k-point mesh). With these files in the same directory, you can start your calculations.
Good luck!
-Nick
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I am focused to study the role of phononic mismatch in the thermal conductivity of two layers interfacing with each other. what will be the most simple method for calculation of thermal conductivity using first-principle calculations?
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Dear Arslan,
if you really want to start from first principles(in DFT) I would suggest you to have a look at the Book -> "Electrons and Phonons" from J.M.Ziman and go an with simplifications wich might fit your problem.
Regards
Ernst
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I have run boltztrap calculations. And i have case.trace file with 10 columns in total. Now I need to plot electrical, thermal conductivities Vs Temprature.
I use to plot with Gnuplot, but when i use :
-> plot 'case.trace' u 2:8 w l
i got a lot of curves in the figure...
here attached my case.trace file.
Could you please tell me the procedure of plotting them with gnuplot?
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Yes, you just change the fixed quantity in '$1' or $2'. For an example: for a fixed temperature if you want to calculate the variation of conductivity as a function of chemical potential then type in gnuplot terminal..
plot "<awk '$2==x' filename.trace" u 1:6 w l
where x is the fixed temperature in kelvin.
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A-0 0 0
B 0.5 0.5 0.5
C 0.5 0.5 0.5
O 0.5 0.0 0.5
O 0.5 0.5 0.0
O 0.. 0.5 0.5
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Theoretically, you can not dope weight percentage. You have to convert weight percentage to atom percentage to dope in the material studio by using the supercell method. For building a crystal unit cell, just follow the CASTEP tutorial which is available in the HELP section in Material Studio. @ Neeraj Kumar Bhoi
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I want a simple method for calculating electron-phonon coupling constant (approximately). Taking advantage of first-principles calculations, not the linear response theory. I hope to change the position of some atoms, calculate ground state energies and eigenvalues, and then estimate the electron-phonon coupling constants. I don't know whether it is feasible or not. Is there such a method?
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The question doesn't make sense, because it's not clear what's the relation between ``first principles'' and the electron-phonon coupling constant.
If you know expectation values of the Hamiltonian it's possible to express the electron-phonon coupling constant in terms of them, assuming the Hamiltonian has some particular form-and to test that this is consistent. This is known as reconstructing a probability distribution from its moments.
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I want to introduce two charged atom in a supercell using first principles calculation (such as ABINIT, VASP). Is it possible? If not, why?
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Dear Uttam Pal
Thank you for your kind reply. I got it.
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My steps is as follows, is there something wrong?
1. create a MAX model-Ti2AlC (directly from database)
2. delete Al atoms from MAX model, obtain bare Ti2C
3. build surface (001), and get a monolayer Ti2C, then put 2 oxygen atoms on both sides.
4.perform structural optimization (only for atom positions)
Should i do structural optimaztion before building surface? Thanks for everyone's help.
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Do not forget the important point in the bulid of monolayers, you must add a vacuum space larger than 20 Å in the vertical direction to prevent the interaction between the neighbouring layers ( after the build surface).
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I'm doing some work with GCMC, but a problem came up.
I want to pack all the residure space in porous material with metal.
(ex. Al, Zn, etc)
It was planed to model the situation of porous material filled fully with metal atoms, using the method like melted metal, ALD.. whatever.
But non-bond forcefield seems not to be appropriate for this purpose. And I'm suffering difficulty in searching for any forcefield of metallic bond.
Is there no way to do this? or shoud I have to do make the forcefield on my own using first principle calculation? Please give me some advice for the problem.
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Hi Seo-Yul,
Classically metallic bonds are difficult to describe accurately. However, there has been good results using potentials developed from tight binding theory. You may find finnis-sinclair or embedded atom model (EAM) potentials helpful for your problem.
Hope this helps,
Jacob
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Dear VASP users,
I am plotting charge density 2D slice for LaVO4 system in VESTA, In 2D plot one scale bar comes in left side which is not showing any value in my case and what represent that ? How does mark corresponding element in 2D charge density plot as in  attached paper for LaVO4.
Over all my query is that how does know which charge density is corresponding to which element in charge density plot and what represent scale bar in left side which is not showing any value. Any other software except VESTA for plotting CHGCAR file.
I have attached snapshot charge density plot for LaVO4  from attached paper like wise I want to plot charge density for my LaVO4 system.
I have also attached 001 2D plot for my LaVO4 system and related CHGCAR file.
Thank you for help and support !
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You can plot 2D charge density by using the '2D data display' option from the 'utilities' tab in the menu bar. Once you click on 2D data display a new window opens up where you can click on 'slice' and enter the (hkl) values corresponding to the plane for which you want to visualize the data. Once you do that the 2D contour is plotted for that plane. There is also an option of choosing 3 atoms and plot the data for that plane created using the 3 selected atoms. The scale of the scalar bar on the left hand side can be chosen under the option 'saturation levels' located below the slice button in the general section. You can set the minimum and maximum values or also in terms of the percentage values based on your requirement.
Side note: To know what values to enter for the (hkl) values so that we can visualize the data on the desired plane I usually prefer to create a new 'lattice plane' (under Edit tab) by entering the (hkl) values.
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I would like to find the k-points for Monoclinic system.
The path follows the trend like this
G-Y-M-C-E-M1-A-X-G-Z-D......etc.
In band structure calculations I have to give k points in this format..
12
G 0 0 0 10 ( this we know)
Y ? ? ? 10 (10 is the points b/w symmetry points )
M ? ? ? 10
C ? ? ? 10
....
..........
.....
My doubt is how to find the Y, M and C points.
Is there any software for all systems or website?
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Kindly visit the site. It is simplest way to find high-symmetry paths. you can see the path also. You just have to upload your POSCAR/xcrysden/quantum espresso input.
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What is the dielectric constant value of alkaline solvent should be taken to investigate the dft first principle calculations using NWChem (COSMO function) or Gaussian?
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Mrs/Miss.,
In addition you should account for the effect of the ionic strength.
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How to calculate bond strength using NWChem; like Wiberg bond indices are used to calculate bond strengths in Gaussian.
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Wiberg bond indices calculation provides bond order which maybe proportional to the bond strength. But Bond strength calculation is possible without doing wiberg calculation. For example if you want to know the strength of A-B bond. Then calculate the energy of AB, A & B (separately). E(A) + E(B) - E(AB) will be the bond strength. You should be careful about the bond dissociation mechanism either it is hetero or homolytic and also basis set superposition error.
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Recently, I've get through a system which has six internal degrees of freedom. I am not aware of internal structural parameters (internal degrees of freedom/free parameters). If it depends on the structure or a choice of lattice, how can i calculate it while doing first principle calculations using VASP code? Any suggestions will be appreciated..
Thank you
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Dear Luitel,
Ya, Thank you very much for your response. The link you attached here gives more than enough information what i wanted to know.
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As deep learning, learning algorithm based on multilayer neural networks, which can figure out regularities in huge data (extracted from experiment), and express them in equations; is developing. How would this development affect computational physics? Will we still be using methods like first-principles calculation etc. as often?
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Dear Abbas, I think this paper could be useful for your analysis of relations between Neural Networks and Computational Chemistry and Physics. Gianluca
G. Montovan, Neural Networks for Computational Chemistry: Pitfalls and Recommendations, 2013
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Density functional theory , first principle calculations, condensed matter physics, material sciences
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Dear Ali,
The spin-orbit is time reversal invariant (this doesn't change Kramers degeneracy) and also has not topological implications. Thus it cannot change an Weyl semimetal in a topological insulator or vice verse, but what can change are the bands behaviour through Dresselhause and Rashba spin-orbit coupling terms which must be included within the Hamiltonian.
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Dear experts,
I think that CaSiO3 has direct and indirect band gap. I am trying to know the direct and indirect band gaps of wollastonite( location of BZ point). A band gab  of 5.022 eV at gamma (G) point  according to LDA (castep code) ( is that direct or indirect band ). There is another interesting minimum conduction band at B point ( is it related to indirect band gap) with valence band minimum at C point . I really need to interpret the results shown in the figure below accurately. any help will be appreciated.   
best regards
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hi, dear. what packge are you using? 
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Dear researchers,
I would like to learn first principle calculation for First-principles study of structural, electronic, and optical properties of cubic III-IV semiconductor. Kindly suggest me good books to start with.
Thank You
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Thank You Sir George C. Giakos.
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I did a calculation based on VASP. The goal is to exact band structure from wannier90 package.
The initial projection for wannier90 is essential, so I used Random initial projections to obtain the wannier functions. But the following convergence of the “Wannierisation” procedure is rather harder. After 7000 iterations, the convergence window is still around 1.0E0.
I think the issue may comes from the initial projection. Then, I assigned the atoms the orbital projection for the initial projection. As a results the num_wann is not equal to num_bands, which is from NBANDS in VASP. However, the convergence of the “Wannierisation” procedure is difficult, too.
So I wander if anyone can offer me some tips? Thanks a lot!!
PS: the system contains 48 atoms,  which presents NBANDS = 184 by default.
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Dear Jiaduo,
The initial projections should be chosen according to the chemical environment/electronic structure of your system of interest. Have a look at: Phys. Rev. B 92, 165134 – Published 30 October 2015 (link attached)
Best regards,
Alberto
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Hi, everyone! When I calculated the properties of two-layer or more 2D nanomaterials, whether I should constraint the atoms of lowest layer or not? and what way should i use, by the Fix Cartesian Position or Fix Fractional position?
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you shouldn't constraint the atoms of lowest layer.
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I need a free software for Windows to perform conceptual DFT analysis like hardness, softness, philicities, and Fukui. Please if you know where I can download any good one left the link in the answer
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For molecular systems, conceptual DFT analysis can be easily carried out by Multiwfn (http://sobereva.com/multiwfn), which is a freely available wavefunction analysis tool. Using this program, you can calculate such as Fukui function, condensed Fukui function, dual descriptor, condensed dual descriptor, local softness and so on. However, first you need to use some quantum chemistry codes to generate input files for Multiwfn. For example, you can use ORCA to generate .molden file, which carries wavefunction information and can be recognized by Multiwfn.
Example of using Multiwfn to perform Fukui function and dual descriptor analyses can be found in Section 4.5.4 and 4.7.3 of Multiwfn manual.
The hardness and softness you mentioned are directly related to molecular energy at different states, you can use quantum chemistry program to directly calculate energies and manually obtain them according to their definitions. For molecular systems there are many free programs can be used, such as ORCA, GAMESS-US, NWChem.
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Hello, researchers.
I'm now studying on the reactions between Al and Fe2O3 by first principle molecular dynamics. I have got the CHG file, then, how to export and display the charge density at different times?
Hope to get your help.
Thanks a lot!
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You can use Python library ASE as well. Here is an example how to extract charges for timeframe "time" to the 3d array "charge". Than you can visualize it with any visualization libary, say from Paraview visualization tool.
from ase.calculators.vasp import *
C = VaspChargeDensity("CHGCAR")
charge = C.chg[time]
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Hello everyone
I want to do optimization of monoclinic structure  with wien2k code. Please give me your suggestion how i can optimize monoclinic structure. 
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If we perform density functional theory (DFT) for any small system consisting of simple Lithium ion(s) under both generalised gradient approximation (GGA) and GGA+U (hubbard) term, in general, what would be the order of change in ground state energy between both the levels of theory?
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As explained by Javier Carrasco, the +U correction is designed to correct the self-interaction error in "strongly correlated" states, i.e. those formed from localised states, such as d and f states. The Li 2s state is relatively diffuse, and I would expect the self-interaction error to be small (hence not strongly affected by a suitable +U correction). More information is provided in the attached paper. 
The relevant issue for lithiated TiO2 is that the lithium will transfer an electron to the Ti 3d-derived conduction band states. The description of these Ti 3d states is affected by the choice of GGA vs GGA+U. Possibly particularly relevant to your question, the intercalation energy will be affected by a +U correction. The second attached paper looks specifically at the effect of adding a +U correction to the Ti d states for Li intercalation into anatase TiO2.
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i.e. the basis equations for geometry optimizations and energy calculations. The equations given for the energy in DFT in the turbomole manual are indeed very less. I need to know the equations in details.
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Hi,
I though that you can start reading this reference:
R. Ahlrichs; F. Furche; S. Grimme.
Comment on ``Assessment of exchange correlation functionals''.
Chem. Phys. Lett., 325(1-3), 317-321, (2000). 
For more specific information for the particular exchange-correlation functionals that you are using the following link could be of help: 
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I am trying to compute the concentration of complex defects using the paper from K. Biswas and S. Lany "Energetics of quaternary III-V alloys described by incorporation and clustering of impurities". (https://journals.aps.org/prb/abstract/10.1103/PhysRevB.80.115206)
If I understand correctly the method, I need to perform the following steps to get the concentration of a complex defect AB:
1) Compute the concentration of simple defects A and B and the concentration of the complex defect AB ;
2) Apply the double-counting correction to the concentrations;
3) Apply the normalisation correction to the concentrations
4) If the concentrations are consistent, stop the process, else, restart from step 2.
I tested this model on a defect with a negative binding energy and I observed that the simple defects concentrations increase with each step and the final result is non physical as I get a complex concentration higher than 1.
It would be of much help if anyone could point out where my error is.
Best regards,
Emmanuel
PS: I have attached a pdf file which shows the first iteration of my calculation if that can help to find my error.
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I juste updated the question with more details and a better example.
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Asking for a friend who doesn't currently have access to researchgate:
I am trying to simulate the optical properties of organic solar cells. i would like to know what functional would provide an accurate result for geometry optimisation of the lattice and optical properties calculation while also being computationally efficient.
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DFT-D for optimization
And HSE06 for electronic proportions Egap
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I am a junior undergraduate, just finished Griffith's quantum mechanics, and also touched a little solid physics(First eight chapters of KITTEL).
I want to know how to calculate the electron distribution in the crystal of sodium chloride from the solution of the Schrodinger equation. If sodium chloride is too difficult, whether the sodium metal can be accurately determined. 
I want to know where I can go to learn these things, and what books to read. Thank you!
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 I do agree with Dr.Daniil Stupin comments
Since most of the calculations which we perform do not take account of the large and small quantum fluctuation in the system.By which we could only able to get a rough estimate value of momentum in the system.This becomes more difficult when we try to solve the Schrodinger's equation in the first excited state other than ground state the scattering of the particle is so large such that one could never a get an exact value in terms of both numerical or analytical either. 
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when i use the quantum espresso to do the converge test for k points test of the scf for metal,but when it comes to calculate the 100 100 100 k points ,it gives a CRASH file :too many k points.as i know for the metal under the same smearing degauss,the number of k points is more ,the Fermi face is more clear in IBZ,but here it told me too many k points and make erro,why?thanx
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Hello
Unless you are using supercluster computing or some very sophisticated computation server your k-pts are much too high!
For systems consisting of even small number of atoms,  when your cell is really small the kpoints mesh should look like 15x15x15 or similar. Therefore I'm asking: do you really need such big mesh of k-pts?
If your answer is YES and  this error is not related to your RAM size then you will need to make some changes in QE source code (look in Modules/parameters.f90) where you can find the max K-pts number.
Regards,
K. Gruszka
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I'm kind of a beginner so please if my question is so easy please excuse that.
I want to know how to model solid state systems. If you have for example a silicon unit cell.
What information do you need to know in order to model the system? 
The cutoff energy and other information that is needed, can you explain that?
and what is the best solid state code?
Thanks
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Dear 
to answer correctly this question, it seem that some other informations on the goal of your work are needed. however, i can reply as next;
to simulate or model a given material in its solid state there are many approach such as the supercell or the clusterthe model.  this choice depends on what you need to model (bulk, surface, grain boundary, thin films, nanostructure, ....). based on your choice for the model the second steo is the selection of the method (DFT, classical, semi-emperical). for each method, there are some needed informations that must be present or given by the user. for DFT method, we need information on the simulated system (atom type, number of atoms, the geometry of the problem, the pseudopotential if needed, ...)
the choice of the code also depend on what you need to do  exactly as well as the selected model.
so, i think that a precise answer need a precise question. finaly, i hope that i have arrived to give you a general view about the problem.
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I have done vc-relax on a simple cubic structure with a=5.4799 having an initial atomic position as:
INITIAL
ATOMIC_POSITIONS Crystal
  0.00 0.00 0.00
  0.25 0.00 0.50, and obtained the final cell-parameters:
 FINAL
CELL_PARAMETERS (alat= 5.47990000)
  0.982742776 0.000000000 0.000000000
  0.000000000 0.960295032 0.000000000
  0.000000000 0.000000000 1.024602826
ATOMIC_POSITIONS (crystal)
  -0.007496170 0.000000000 0.000000000
   0.257496170 0.000000000 0.500000000.
Please, If I set ibrav=0, how can I obtain lattice parameter (a); and which of these atomic positions is suitable for use because I am just a novice in this field of study.
Thanks
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To get lattice parameter you have simply to multiply (alat= 5.47990000) with a,b and c in the matrix of cell parameters.
but I think that you should define crystal symmetry first because it looks like the software didn't detect the symmetry.
when you define crystal symmetry you will get a=b=c but with different value due to pressure. 
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Someone could give me a tutorial in VESTA that allows me to learn how I prepare a slab for DFT computation in order to simulate a surface calculation to see the atomic and electronic structure of surface.
This is my first attempt , please help.
Thanks in advance.
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Dear Firas,
This is a nice tutorial on how to prepare an input file for surface calculation using vesta.
Best of luck.
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Hello,
I am running first principles calculations on indium gallium zinc oxide system.  The average bond length value that I have obtained is 1.99 Å, whereas in literature, a similar calculation has resulted in average bond length value of 1.79 Å.  Is this diifference significant? 
Is there some literature available that contains some guidelines as to what the range of this variation should be.
Thanks,
Divya
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Thank you.
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Dear all,
I know there is a software called SRIM, which can calculate the dose depth profile. Also,  the pre-irradiation and post-irradiation properties can be compared and evaluated by many experimental techniques such as nano-indentation, in situ X ray micro-diffraction, Tof-SIMS, SEM and TEM. In addition, first-principles simulation and kMC can be used to simulate the bulk and grain boundary diffusion of some fission products like Ag, Cs, Sr and Eu. What I would like to ask is, however, the kinetic process regarding the nuclear materials, for example the diffusion under irradiation. Does someone have relevant research experiences or can you recommend some references for me?  
Any suggestions are appreciated.
Thanks in advance!
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Hi Cheng,
Determining radiation effects on materials, their properties and their overall performance is a multi-scale problem.  The simulation approach often depends on the material properties you seek to evaluate. It also depends on the type  of radiation being used and the energy of the radiation particles. For example, gamma rays interact with the electrons whereas neutrons interact directly with the nucleus. Furthermore, the radiation dose is also something you may want to take into consideration.
Without knowing the details about your problem, I will attempt to answer your question assuming there is significant radiation damage due to energetic particles impinging on the material of interest.
In your case, one approach I would recommend is to you start out with DFT calculation of the crystalline structure with arbitrary defects in the structure to mimic radiation damage. These defects may include vacancies or interstitials placed at random in your simulation cell. Then you can use the nudged elastic band approach (after determining the stable binding sites) to find the energy barriers and the frequency for the atom of the species of interest hopping between the different sites. You can then use your results in a kinetic Monte Carlo simulation to determine the diffusion coefficient which can ultimately be used in the diffusion equation to evaluate the effect of radiation on the evolution of the concentration profile in your material. 
Another, perhaps simpler approach is to use Molecular Dynamics simulations to calculate the diffusion coefficient. Here, you will again build a simulation cell with defects to mimic radiation damage effects, but you can then use the simulation cell immediately in an MD simulation and determine the diffusion coefficient. You can then still use the diffusion equation as before to evaluate radiation effects on the evolution of the concentration profile. If you decide to use an MD simulation (and LAMMPS is a great option for that and is an open source code), then using SRIM can help you determine the size of the cell to use in your simulation depending on the type and energy of the irradiation particles.
I hope this helps. 
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Topological insulator consists of bulk insulator state and surface metal state. When I obtain its effective dielectric constant (either experimental measurement or the first principle calculation), how to separate the contribution from bulk state and surface state? In the paper Nat Commun 2014, 5, 5139, the authors use Tauc-Lorentz formula and Drude formula to fit bulk and surface contribution, respectively. I am not clear how to involve the thickness of surface state in the fitting process. Can anyone help?
Thank you very much.
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Can you please tell me how you are performing the measurements? Which is the equipment you use and which is the measuring set-up?
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I have seen that there is significant difference between the total DOS of the system and PDOS of the system. The intensity of TDOS is found to be higher than the intensity of PDOS (after addition of projected density of states). Why?
Secondly, I have found that the magnetic moment in OSZICAR is not consistent with the value of magnetic moment given in the OUTCAR. The value of magnetic moment given in OSZICAR is always larger than that of OUTCAR. Why?
Thirdly, which value of magnetic moment is correct one?
Can we calculate magnetic moment from the difference of spin up and spin down DOS? If yes, then how can we calculate magnetic moment from DOS?
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Hi Muhammad
Fernando is right in matter of TDOS and PDOS difference.
I just would add some infomation on magnetic moments. The value of magnetic moment that you have in OSZICAR is the total magnetic moment of the cell obtained from summation overall space. OUTCAR contains magnetizations obtained form an integration of the spin densities in the atomic spheres with given radii r=RWIGS. Due to the fact that the total volume of spheres is not equal to  the volume of the cell, these values (given in OUTCAR and OSZICAR) is not equal to each other. I think the correct total value is given in OSZICAR. You also can use the Bader code to obtain correct magnetic moments in each atom. 
The difference of spin up and spin down DOS can give you spin pollarization only. If you devide this difference as (up-down)/(up+down) you get spin polarization in %.
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I have done elastic constant calculation using IBRION=6. I have used the following script (.pbs file). I got the output as SUMMARY.fcc. I have plotted the output as 1.tiff but I donot get the result as expected. I am confused how to proceed ahead. Kindly help me. I think there is problem in .pbs file.
Thanks
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Dear Ashish,
Read the attached papers carefully will sort out all your questions. 
Best
Roshan
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Dear Experts
Form results of BoltzTraP with no carrier concentration. Please help me to plot quantities such as Seebeck vs. carrier concentration. (case sample Si.trace)
1. What is SI unit of Number of carrier per unit cell volume?.
2. How to converse Number of carrier per unit cell volume to carrier concentration (in unit cm^3)?.
Best Regrads
Meena Rittiruam
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Dear Meena Rittiruam
2. to convert number of carriers per unit cell volume to carriers concentration (in unit cm^3), you just have to divide the number of carriers per unit cell by the volume of the unit cell expressed in cm^3...
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Hello,
I'm studying the effect of varying the Li concentration in LixMn2O4 (x=0-1), I calculated the relax lattice constant and get acceptable results, but I haven't been able to calculate the intercalation voltage for different concentration of Li.
I'm using the following procedure:
V(x) ≈ - ΔE/(xj-xi)e (xj = 1, xi = 0)
ΔE = E[LixMn2O4] - E[Mn2O4] - E[Li]
E[ ] is energy/formula unit
I had tried without relax, relaxing each LixMn2O4 and Mn2O4 structures and also only relaxing LiMn2O4, but the results aren't congruent with previous publications.
I'm using as reference the paper
Factors affecting Li mobility in spinel LiMn2O4—A first-principles study by GGA and GGA+U methods, Bo Xu, Shirley Menga, Journal of Power Sources 195 (2010) 4971–4976
I'm using simulation package VASP and I'm doing GGA and GGA+U calculations
INCAR that I have used
Anyone has some experience with this types of calculations?
How can I get the voltage?
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