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# Computational Materials Science - Science topic

Explore the latest questions and answers in Computational Materials Science, and find Computational Materials Science experts.

Questions related to Computational Materials Science

I'm trying to do geometry optimization of KAgO3 perovskite material in the material studio using CASTEP by setting cutoff energy 500 ev and various k points 888,999,101010,121212. but every time it fails showing the messages mentioned in the pictures. What is the possible reason and solution for successful optimization?

need an explanation from experts. Thank you.

#Material_studio #Geometry_optimization #Failure

I have a 3D orthogonal woven composite structure with warp, weft, and binder yarns oriented in three directions. After modeling these yarns, I imported them into Abaqus as parts. I modeled the yarns as solid elements and assigned their material properties, including elastic, density, and Hashin damage properties, to each section. For meshing, I used C3D8R elements for each yarn. I set up the appropriate impact conditions. However, I am encountering an issue with the Hashin damage model. In Abaqus, I consistently receive the error message: "Hashin damage initiation criteria cannot be used with element 1 instance binderyarn-1-1."

Could you suggest any strategies to model this using the Hashin criteria without implementing a UMAT subroutine? How can I resolve this issue?

When I optimize the structure, there is a difference in energy with and without LORBIT tags under exactly the same conditions.

Does anyone know why there is this difference?

Hello dear researchers, I hope you are doing well.

I want to ask you a question. I have a unit cell with 24 atoms (4 A, 4 B and 16 X) and I want to substitute X atom by another atom (for example changing one X by other element).

My question is, can I substitute it within the unit cell without making supercell?? or should I make a supercell??

Hello,

I am investigating charge mobility and scattering rates using EPW software, but I am not sure how to do the convergence test. Is the decay sufficient or do I need to monitor the changes in mobility and scattering rates with changes in other input variables? ( which other properties can be used to confirm convergence?) Again, which input values/variables do I need to optimize?

I am very new with CASTEP simulation. Can you please help me out with the general steps for geometry optimization?

(1) Build unit cell > geometry optimization > cleave > supercell > optimize again> band structure and optical calculation

(2) Build unit cell > geometry optimization > cleave > supercell > band structure and optical calculation

(3) Build unit cell > geometry optimization > band structure and optical calculation
If I go with (1) the simulation runs indefinitely. With (2), after oftimization, cleaving and supercell when I try to run bandstructure and optical calculation, an error message show saying "There are no CASTEP input or output files available. CASTEP input and output files from a previous run are required in order to perform a properties run."
With (3) everything runs perfectly but this is only a unit structure and not a supercell.

Please advice

How can we use DFT to study how various defects impact the optical and electronic properties of semiconductors like CIGS chalcopyrite materials?

I've been working with DFT-VASP and have a few questions regarding the calculation of screened/unscreened plasma frequency.

I'd like to outline my workflow and the parameters I've used, and I'd appreciate it if someone could confirm whether this approach is correct or suggest any necessary adjustments.

**Workflow:**

**Geometry Optimization:**I initiated the process with a 6x6x6 k-grid.**SCF Calculation:**I performed a self-consistent field (SCF) calculation to generate the CHGCAR and WAVECAR files.**Optical Property Calculation:**To calculate the plasma frequency, I'm planning to use the LOPTICS = .TRUE. option with denser k-grid (18x18x18).

**INCAR File:**

**ISTART = 1****ICHARG = 11****LOPTICS = .TRUE.**(to write optical properties in OUTCAR file)**ENCUT = 450****NELM = 100**(maximum number of electronic steps)**EDIFF = 1.E-05**(energy stopping-criterion for electronic iterations)**EDIFFG = -0.02**(force stopping-criterion for geometry steps)**NSW = 0**(maximum number of geometry steps)**IBRION = 2**(ionic relaxation method)**ISIF = 2****ISYM = 1****POTIM = 0.05**

is this workflow and the INCAR file correct? is it correct to user denser K-grid for optical properties?

I have a structure at the ground-state exhibiting different random regions of FM and AFM arrangements, how to calculate the curie temperature knowing that calculating 'J' is not applicable?

Dear all,
I am pretty new to Quantum Espresso and Wannier90. After finding out the bandstructure of my system using QE, I am trying to find out the wannier interpolated band structure, but these two band structures show a significant discrepancy. I have tried changing the projection and disentanglement window, but I am not getting a better result. The input files and bandstructure plots can be found here https://drive.google.com/drive/folders/1kxI7TZ4UD4x3TlCX8vT-J2WVLzm0nBTX?usp=sharing . It might be a minor solution for the experts. Hoping to get a positive response. Thank You.

Hello, I am interested in the simulation of island growth by the deposition of adatoms. As a beginner, which software is better to use; for example, the open-source MOOSE framework or COMSOL multiphysics? Thank you in advance.

Hello everyone. I am new to quantum espresso and trying to do band structure calculations. I have done the same band structure calculation using

**VASP**. In VASP we can set the KPATH**as follows***Γ—X—P—N—Γ—M—S|S0—Γ|X—R|G—M*K-Path Generated by VASPKIT.

20

Line-Mode

Reciprocal

0.0000000000 0.0000000000 0.0000000000 GAMMA

0.0000000000 0.0000000000 0.5000000000 X

0.0000000000 0.0000000000 0.5000000000 X

0.2500000000 0.2500000000 0.2500000000 P

0.2500000000 0.2500000000 0.2500000000 P

0.0000000000 0.5000000000 0.0000000000 N

0.0000000000 0.5000000000 0.0000000000 N

0.0000000000 0.0000000000 0.0000000000 GAMMA

0.0000000000 0.0000000000 0.0000000000 GAMMA

0.5000000000 0.5000000000 -0.5000000000 M

0.5000000000 0.5000000000 -0.5000000000 M

0.3248084690 0.6751915310 -0.3248084690 S

-0.3248084690 0.3248084690 0.3248084690 S_0

0.0000000000 0.0000000000 0.0000000000 GAMMA

0.0000000000 0.0000000000 0.5000000000 X

-0.1496169380 0.1496169380 0.5000000000 R

0.5000000000 0.5000000000 -0.1496169380 G

0.5000000000 0.5000000000 -0.5000000000 M

But I am not being able to do the same in

**quantum espresso**. When I try to set the KPATH in QE as follows, the result shows a continuous path as opposed to the breaks in**.***S|S0, Γ|X, and R|G* K_POINTS { crystal_b }

13

0.0000000000 0.0000000000 0.0000000000 10 !GAMMA

0.0000000000 0.0000000000 0.5000000000 10 !X

0.2500000000 0.2500000000 0.2500000000 10 !P

0.0000000000 0.5000000000 0.0000000000 10 !N

0.0000000000 0.0000000000 0.0000000000 10 !GAMMA

0.5000000000 0.5000000000 -0.5000000000 10 !M

0.3245757930 0.6754242070 -0.3245757930 10 !S

-0.3245757930 0.3245757930 0.3245757930 10 ! S_0

0.0000000000 0.0000000000 0.0000000000 10 !GAMMA

0.0000000000 0.0000000000 0.5000000000 10 !X

-0.1491515861 0.1491515861 0.5000000000 10 !R

0.5000000000 0.5000000000 -0.1491515861 10 !G

0.5000000000 0.5000000000 -0.5000000000 10 !M

I think I am doing something wrong when setting up the K_POINTS { crystal_b }. Any help or suggestion is highly appreciated. Thank You.

I am facing an issue when calculating the dielectric function of Aluminum doped zinc oxide.

I am trying to replicate a paper and the imaginary part of the dielectric function is correct like in the paper I am trying to validate.

However , the real part of the dielectric function at the low energy region (0 to 0.5) should be negative, I am obtaining positive values, it seems that this part is reversed for some reason.

The rest of the real part data is correct.

I am using GGA- PBE- Norm conserving ultrasoft pseudo potentials.

I am really confused as I checked the documentation and it seems that the real part is calculated from the imaginary part, so how come I am getting these reversed values if the imaginary part is correct?

Thank you so much in advance.

I have been searching for information on the crystal structure of CH3NH3GeCl3 in the trigonal R3m space group, but have not found any information on the atomic position or CIF. I searched various databases, such as COD and Materials Project, but found no relevant results.

While I have found the CIF of MAGeCl3 in the Pnma space group, which crystallizes in low temperatures, I am specifically interested in the R3m phase of CH3NH3GeCl3 at high temperatures.

It would be greatly appreciated if anyone has any information on the R3m CIF for CH3NH3GeCl3 (MAGeCl3), or any related materials such as MAPbI3.

With 12 atoms, it run. But when I increased to 96 atoms, also increasing nbnd, ecutwfc, ecutrho, its showing error:

....

**Band Structure calculation**

**Davidson diagonalization with overlap**

**c_bands: 3 eigenvalues not converged**

**c_bands: 2 eigenvalues not converged**

**c_bands: 1 eigenvalues not converged**

**c_bands: 3 eigenvalues not converged**

**c_bands: 1 eigenvalues not converged**

**...**

**After that the program stopped. The screenshot and the input file is given as attachment.**

I am trying to find out the

**topological hall effect**for my system of study. I currently have no idea about the process and what software packages to use. I know that we can find the**anomalous hall effect (AHE)**using the Wannier90 package. Any suggestions regarding this will be greatly appreciated.Hello dear researchers.

Please, how do I know that I have done a good optimization of the structure (I use abinit), should I see something in the output file or just compare the cell parameters with the experimental values?

Thank you in advance.

Sincerely.

Hello dear researchers

I am beginner in Abinit software, I made a simulation of piezoelectric properties and I got its two errors. Please if you have any idea how I can solve them please.

-----------------------------------------------------------------------------

ddb_piezo : WARNING -

Acoustic sum rule violation met : the eigenvalues of accoustic mode

are too large at Gamma point

Increase cutoff energy or k-points sampling.

The three eigenvalues are: 2.589265E-05 2.380597E-05 2.589265E-05

ddb_piezo : WARNING -

Unstable eigenvalue detected in force constant matrix at Gamma point

The system under calculation is physically unstable.

-----------------------------------------------------------------------------

Hello dear researchers

I am confused, I calculated by DFT the dielectric tensor as a function of frequency for BaTiO3 and found a value of the dielectric constant which is 6.5, while in the experimental studies they studied this constant as a function of temperature and they found values in the order of 6000.

My question is: is there a difference between the theoretical and experimental dielectric constant? Is it normal to find such values or have I made mistakes in the DFT calculation ???

Hello dear researchers.

I would like to know how to determine the number of bands of a compound ????

Thanks in advance.

I am searching for the CIF file of NiCo layered double hydroxide (NiCo-LDH). I have searched on the available online resources but could not get the file.

The CIF file for Ni

_{1}Co_{1}-LDH is high requested.Hello researchers,

I am new to wannier90, and I am currently trying to run a

*wannier.2.1.0*calculation through*vasp 5.4.4*interface. After the DFT run, the files*are generated successfully but when I try to run "***wannier90.up.eig, wannier90.dn.eig, wannier90.up.amn, wannier90.dn.amn, wannier90.up.mmn, wannier90.dn.mmn***wannier90.x wannier90.win*it shows "No wannier90.eig file found. Needed for disentanglement". How to I generate wannier90.eig? Should I just combine wannier90.up.eig and wannier90.dn.eig?**"**Is it hard to learn Molecular dynamics (MD) simulation? Do you have a suggestion for learning?

Dear researchers,

I'm working on multi-atomic inorganic compounds. So, visualization of atoms in a particular plane becomes difficult. As a result, it is difficult to calculate plannar density (PD) manually. So, please suggest me a way/software to calculate PD easily.

Thanks in advance.

Regards,

Lakshaman

I have an idea to run some computational phase diagram codes on OpenCalphad , for a rather strange purpose

I have downloaded OC6 on windows 10, skimmed the user manual, browsed the GitHub page(https://github.com/sundmanbo/opencalphad), but nowhere found a simple code like finding equilibrium diagram for a binary alloy or ternary alloy at a given temperature. Googling is in vain, unfortunately.

Can any of you provide a simple step-by-step guide towards such simple to progressively complex problem?

I have found OC user manual to be not too user-friendly or pedagogically understandable to me.

I need the value of double partial differentiation of Gibbs energy (d^2G/dX^2)_eq at the equilibrium of a system. Does thermocalc/pandat calculate this term? If not, how can I get it from thermodynamic database?

Is there any way to convert the interaction energy among two systems into force?

I have two systems, wherein the 1st system destroys the configuration of 2nd system, owing to electrostatic interactions. What I suppose is that the 1st system is providing a certain amount of force that exceeds the total amount of energy required to hold the 2nd system in that specific configuration.

Hello everyone, I am currently working on a Heusler alloy system which has a

**non-collinear**magnetic order as reported by a earlier study. I intend to further explore this non-collinear magnetic state. It would be really helpful if someone can suggest me some properties that can be investigated**theoretically**in order to see if it has a potential use in spintronics devices or if it has some kind of other applications. I am using VASP. Thank you.How to calculate ΔG = ΔE + ΔEZPE - TΔS + ΔGpH + ΔGU, computational hydrogen electrode (CHE) model introduced by Norskov, the Gibbs free energy change (ΔG), using CASTEP code?

hello everyone, I am currently working on a Heusler alloy that has a very low spin polarization (below 10%). Can it still be used in spintronics devices? (usually higher spin polarization is preferred for spintronics application). Also, I should add that the antiferromagnetic state of the compound has almost twice the Magnetocrystalline Anisotropy Energy as compared to the ferromagnetic state (which is THE energetically stable state for the compound).

Hello Everyone,

In many materials we can observe linear band crossing even above or below the fermi level. So what is the importance of having DIrac points somewhat away from fermi level (lets say around 2eV) ?

Can any crossing of bands which is linear leads to a DIrac point ?

Hey,

Please share your work on UMAT and resources (except popular imechanica tutorial).

Thanks.

Hello all, I am currently working on a system that contains Pt, and when I've plotted the 2D ELF pattern, this kind of plot was obtained. So, is there any kind of explanation for these kinds of plots?

Hello. Can anyone please tell me how to set INCAR/POSCAR for AF1, AF2 magnetic structure calculation, introducing different magnetic ordering for different planes? I tried making the POSCAR file using VESTA but I am not being able to turn off the symmetry completely. I thought if I turn off the symmetry I can set MAGMOM for each individual atom of a certain plane in the INCAR file but I am not being able to do so while creating the POSCAR file using VESTA. VESTA automatically fills up each corner position of the unit cell due to symmetry and therefore when I set MAGMOM in the INCAR file, one value of MAGMOM covers all the corner points, hence not being able to set different value/direction for different corner atoms

Hello

Kindly refer the free energy functional for systems with elements A-B and A-B-C, in the attached image.

My question is, why the gradient of the dependent element (A) appears in multi-component system (2), while not considered in binary system (1)? It would be also better if you attach any references for derivation of (2).

Thank you!

I'm looking to simulate solidification following the Scheil model with back-diffusion in Pandat. I see, however, that a separate set of databases with .sdb format is required. Is this something that I have to get access to from somewhere or is it something that I need to create?

Hi, I've been an experimentalist throughout my career and I want to add to my knowledge and expertise in Materials Science by delving into computation, modeling and simulation. However, I'm very confused about where to begin as it appears that field of modeling and simulation is quite vast and expansive. If I had to choose a starting material type, I'd say composites and modeling of failure modes of composites. Can anyone guide me on where to begin? I'm a complete novice when it comes to anything computational. Where do I begin, if I'm starting from scratch.

I am currently doing my postdoc and planning to join some institute as a faculty by the end of this year.

My entire Ph.D. and postdoc durations were 95% experimental and 5% simulation. However, I am scared that if I join a new place as a faculty it will take so much time and resources to build an experimental lab from scratch. Hence, I am planning to learn some MD simulations (through a friend of mine who has a lot of experience) to kick start my research (in less time and resources) by the time the experimental lab is ready in the new university.

I need some suggestions from the experienced professors and postdocs in this thread about the possibilities, failure chances, risks involved, the correctness of Decisions.

The image is fed into MATLAB, The absolute value part of DFT of R,G,B pixels are separately determined, and the root-mean square value (RMS) of three DFT matrices (elementwise) are plotted into logarithmic contour plot (origin shifted to center) . The DFT contour plots have too much noise, but the version of MATLAB I use has no Gaussian filter available. The actual images are to the scale, and I want particle size distribution from the RMS-DFT.

I have already tried thresholding, but thresholding does not keep image of distinct grains distinct, and so the thresholded image is beyond recognition for grain size determination.

Without consulting the phase diagram (of still unexplored alloy systems) , how one can predict which alloying addition in an element would produce intermetallics with some given compositions? For example,

*how would one say that C is (one of the ) most crucial alloying element of Fe and Si of Al, with just consulting the periodic table and electronic structure*? Of course, there is no objective definition of "most useful" alloy- the same alloying element raising strength would not be the one that raises ductility.Some special properties can be reasoned as

- Strength and ductility- estimable by formulae for Solid solution, precipitation, dispersion and grain boundary strengthening- but
**how to physically link solid solution strengthening or Pierres-Nabarro stress of an alloy from electronic structures? Can ductility in these cases also be estimated from first principles?** - As for thermal and electrical properties, t
**he phonon/electron scattering data may be generalizable for a bigger group of alloys to find out thermal and electrical conductivities- but how**? The conductivity drop can be compared between solid solutions and intermetallic formers, but how to be sure that the alloy formed would be of any calculated phase distribution and of this certain electrical conductivity from first principles? - Corrosion resistance- The Pilling-Bedworth ratio is related to adherence of oxide or other protective films of metal- but
**how alloy composition can be related to strength, adherence and composition, and ultimately, reactivity of the protective film**? Relative position of EMF series can be, of course, estimated from total lattice energy, ionization energy and hydration energy.

I have just mentioned the two extremes of intermetallic formation and complete immiscibility- (complete miscibilities are well explained by hume-rothery rules, and ultimately also depends on how one objectively measures electronegativity), because there is, to my knowledge, no concrete rules to predict nature of phase diagram (isomorphous or eutectic or peritectic or monotectic or...) between two elements, let alone two compounds.

While electronic band structures of an element are available to be computed by standard methods, there is no systematic way to predict crystal structure or computed thermodynamic properties from composition alone (that are vastly generalizable).

I think there are scientific factors like cosmic and geological abundance, position in EMF series (and hence ease of extraction) as well as socioeconomic factors like market demand as choice for an alloying element. But is it possible to locate useful alloying elements for any of the elements with same unified rationale? (say of Mo, Ru, Rh, Pm, Tl)

And again, is there seemingly any way to tell which pair of metals or elements would be completely immiscible in solid states?

In theory, it is all about minimizing gibbs free energy, and from specific heat data of a solid, one can extract both values of enthalpy and entropy term. If this technique is generalizable for any solid, then why it is not used pervasively? is it because we just cannot predict the specific heat without crystal structure, and from chemistry alone, there is no way to predict crystal structure?

**Is it not possible to obtain Gibbs free energy of overlapping electron orbitals solely from schrodinger's equation, just like total energy is extracted from eigenvalues of Hamiltonian?**Hume-Rothery rules or Darken-Gurry maps are good starting points, but not good enough. Machine-learning based prediction can make things more systematic but without potentially answering the "why"s in a language familiar to humans .

**Interatomic potentials are scarce and very rarely generailizable**for any group of elements (like Lennard-Jones for gases). My question finally boils down to-**prediction of effect of alloying of any two elements, and ultimately composition to crystal structure and phase diagram calculation from first principle- is it even partially possible, if yes, how?****....................................................................................................................................**

*P.S: Honorable Researchers, Please provide related research papers related to these questions, along with your valuable feedbacks. I am unashamedly open to admit my severe incompleteness of knowledge, and I am far from being master of these field of science. SO feel free to point out where I have mistaken, and also*

**show me approach to synthesize such vast scientific knowledge into a coherent framework.**

*.............................................................................................................................................*See some of my related questions

- https://www.researchgate.net/post/What_can_be_theoretical_reason_for_these_patterns_of_Crystal_structures_in_periodic_table?_ec=topicPostOverviewAuthoredQuestions&_sg=qQHz-0jUZMihIai8gwUp1voPk-Tw5-YCl59uQgT88757TE3f6VQz9s6UGLULozUurbHcPQ3VJnXpw-YC
- https://www.researchgate.net/post/Is_there_any_special_rule_to_find_out_possible_room-temperature_stable_silicates_chemical_composition_if_not_crystal_structure_itself?_ec=topicPostOverviewAuthoredQuestions&_sg=qQHz-0jUZMihIai8gwUp1voPk-Tw5-YCl59uQgT88757TE3f6VQz9s6UGLULozUurbHcPQ3VJnXpw-YC
- https://www.researchgate.net/post/How-etchant-for-a-particular-alloy-system-is-developed-Can-it-be-estimated-from-first-principle-physics-chemistry-and-metallurgy?_ec=topicPostOverviewAuthoredQuestions&_sg=qQHz-0jUZMihIai8gwUp1voPk-Tw5-YCl59uQgT88757TE3f6VQz9s6UGLULozUurbHcPQ3VJnXpw-YC
- https://www.researchgate.net/post/What_are_the_factors_molecular_crystalline_structure_related_that_affect_refractive_index_of_ceramics_glasses_and_polymers_How?_ec=topicPostOverviewAuthoredQuestions&_sg=qQHz-0jUZMihIai8gwUp1voPk-Tw5-YCl59uQgT88757TE3f6VQz9s6UGLULozUurbHcPQ3VJnXpw-YC
- https://www.researchgate.net/post/How-computational-phase-diagram-techniques-can-find-Gibbs-free-energy-of-a-crystalline-phase?_ec=topicPostOverviewAuthoredQuestions&_sg=qQHz-0jUZMihIai8gwUp1voPk-Tw5-YCl59uQgT88757TE3f6VQz9s6UGLULozUurbHcPQ3VJnXpw-YC
- https://www.researchgate.net/post/How_can_symmetry_of_a_crystal_can_be_found_out_from_solely_electronic_structure_of_constituent_atoms?_ec=topicPostOverviewAuthoredQuestions&_sg=qQHz-0jUZMihIai8gwUp1voPk-Tw5-YCl59uQgT88757TE3f6VQz9s6UGLULozUurbHcPQ3VJnXpw-YC
- https://www.researchgate.net/post/How_binary_solution_models_were_derived_from_first-principle_thermodynamics?_ec=topicPostOverviewAuthoredQuestions&_sg=qQHz-0jUZMihIai8gwUp1voPk-Tw5-YCl59uQgT88757TE3f6VQz9s6UGLULozUurbHcPQ3VJnXpw-YC
- https://www.researchgate.net/post/How_crystal_structure_of_a_one-element_metallic_molecular_crystal_under_a_given_T_P_can_be_estimated?_ec=topicPostOverviewAuthoredQuestions&_sg=qQHz-0jUZMihIai8gwUp1voPk-Tw5-YCl59uQgT88757TE3f6VQz9s6UGLULozUurbHcPQ3VJnXpw-YC
- https://www.researchgate.net/post/What-decides-lowest-free-energy-crystal-structure-of-a-solid-at-a-given-temperature-and-pressure?_ec=topicPostOverviewAuthoredQuestions&_sg=qQHz-0jUZMihIai8gwUp1voPk-Tw5-YCl59uQgT88757TE3f6VQz9s6UGLULozUurbHcPQ3VJnXpw-YC
- https://www.researchgate.net/post/Why-metal-valency-affects-mutual-solubility?_ec=topicPostOverviewAuthoredQuestions&_sg=qQHz-0jUZMihIai8gwUp1voPk-Tw5-YCl59uQgT88757TE3f6VQz9s6UGLULozUurbHcPQ3VJnXpw-YC

Thank you very very much to hold your patience to read the whole post :)

I have created an Ice 1h crystalline structure and an Aluminium substrate structure and equilibrated both at 250K. Now I need to bring them together in a way that an adhesive bond is created. Reading the literature I have found that this can be achieved by an

**energy minimization process to bring the structure in contact and thereby inducing artificial stress at the interface**that can then be relaxed and a nucleation process can be started; but I don't grasp how this is done in LAMMPS.Any insight is appreciated.

As I was tweaking step-by-step OpenCalphad6 Macros step1.ocm involving phase and thermal property calculation of a High-speed steel, I could not incorporate more than 6 elements in the steel formula. Upon reading the OC6 Command-Line Interface, I came to know that, it was taking the element values from a database (SGTE SSOL2 database from 2001 for 6 elements) that contained only the six elements. How can I can any elemet in the steel as i wish during this kind of simulation?

Suppose one needs to find out room-temperature stable silicates chemical composition of a particular cation, suppose magnesium. Is there any rule to estimate which stoichiometric values of metal oxide: silica ratio would stabilize the binary silicate at room temperature? (i.e. in this example, how would I find out only Forsterite and Enstatite are of stable ratio, without empirically studying MgO-SiO2 phase diagram?)

At a first glance, the ratio seems to be consisting of any possible prime(and 1) numbers. Since its crystal structure is not known, Pauling's Rules also cannot be applied step-by-step to find out where silica tetrahedra are sharing corners, edges or faces.

Theoretical Computational and numerical simulation of phase diagram obviously can find out the stable ratios, but this is not what I ask for. I ask for tolerably simple chemistry rules like those provided by Hume-Rothery, Pauling or Goldschmidt, understandable with freshmen/sophomore chemistry/materials science/mineralogy knowledge.

I am currently using Quantum ESPRESSO to determine the minimum distance where the interaction between two nickel atoms becomes minimal. To do so, I set up a cube with two nickel atoms inside, one located at the origin and the other one along the body diagonal. For each calculation, the other nickel atom becomes farther from the one at the origin by an increment (0.5 angstrom).

Here is the sample quantum espresso input file:

&control

calculation = 'scf',

restart_mode='from_scratch',

prefix = 'ni_sep',

outdir = './outdir',

pseudo_dir = '<redacted>/GBRV',

verbosity='high',

/

&system

ibrav=1,

A=12.0,

nat=2, ntyp=1,

ecutwfc=90,

ecutrho=720,

occupations='smearing',

smearing='gaussian',

degauss=0.01,

nspin=2,

starting_magnetization(1)=0.3,

/

&electrons

electron_maxstep=300,

conv_thr=1D-9,

mixing_beta=0.7,

mixing_mode='TF',

/

ATOMIC_SPECIES

Ni 58.693 ni_pbe_v1.4.uspp.F.UPF

ATOMIC_POSITIONS {angstrom}

Ni 0.000000 0.000000 0.000000

Ni 3.464100 3.464100 3.464100

K_POINTS {automatic}

11 11 11 0 0 0

The problem is that the calculation runs more than 10 hours in my machine. I would like to ask for help in optimizing the input file. Thank you

I want the density profile of a solvent in a particular direction when we have the trajectory file from molecular dynamics simulation. For example, analyzing the solvent density around a protein of interest or a graphene sheet. I have attached a similar analysis from a paper where you can see the density profiles below the trajectories.

Thank you!

Hi, I am trying to solve the motion of bubbles. The argen gas are injected from an inlet into liquid steel. Therefore the air generates the bubble. For the bubble motion I used DPM model and for the liquid steel, molten slag and top gas, I used VOF model.Now for the last step of my project I have to delete the bubble as soon as they impact the top gas. I wanna deleting bubbles with UDF.The idea for this UDF is that I want to delete the bubbles when they arrived at the position that the volume fraction of top gas is larger than 0.5. This is the UDF I am using:

#include "udf.h"

#include "dpm.h"

#include "sg_mphase.h"

DEFINE_DPM_SCALAR_UPDATE(stream_index,c,t,initialize,p)

{

cell_t c;

thread *t;

Thread *gas;

gas = THREAD_SUB_THREAD(t,2);

if(C_VOF(c,gas)>=0.5)

p->stream_index = -1;

}

Thanks.

I am good at DOS, Band structure and phonon studies. I would like to extend my studies to Dielectric and Ferroelectric studies. How to find the polarization in the material?

I am new to material simulation and I am willing to learn the theoretical aspects like what is k point mesh, how to interpret band diagram, how born charge results in IR spectra etc. I have experience of using DFT using gaussian 16 (modeling of reaction machnism) but don't have any experience in material simulation.

Thank you in advance.

In materials science, a

**dislocation**(line defect) represents a linear crystallographic defect within the crystal structure, which causes an abrupt change in the arrangement of atoms, which in turn influences several properties of materials. The**dislocation density**is a measure of the number of**dislocations**in a unit volume of a crystalline material usually having unit of lines per square meter (lines/m^{2}).Voids, pinholes, cracks, or inclusions like

**bulk defects**are the macroscopic regions, where there are no atoms and which can be thought of as clusters of vacancies. Usually, bulk defect density has the unit of per cubic centimeter (cm^{-3}).However, I would be highly obliged if any scholar provides me articles or mathematical equations (if any) to relate the dislocation density to the bulk defect density.

Thanks in advance.

I changed some of the Sn atoms' composition to 50%Sn and 50%Sb in the Co

_{2}TiSn 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?

Hi, i'm a physics student working in a project of materials science. I'm doing a simulation using LAMMPS.

In this case, i have a problem with the error Lost atoms: original 60536 current 56624 (../thermo.cpp:427) once i run the script. I'm trying to put a graphene sheet in a fix nvt 10 kelvin. But once the fix it's running, in 4 steps the velocity becomes irrational and I get the error.

Can you please guide me please? I'm new in all this.

Thank you for the help.

Dear Respected Members,

I did many tests to construct antiferromagnetic (AFM) ordering, which seems so hard to achieve. I build supercell of 2x2x1 containing 32 atoms of Mg16O16, and then replace two of Mg atoms by Cu atoms to get 12% Cu doped MgO (Mg14Cu2O16). My goal is to get the energy deference between the two configurations ΔE=EAFM−EFM from CASTEP code. Please check out the attached figures that I did and links to interpret the results using CASTEP code in materials studio. Please I need your experience and your valuable comments that will really put me on the right track. thanks.

the paper that I follow is "Ferromagnetism in Cu-doped MgO: Density-functional calculations"

DOI 10.1016/j.ssc.2014.06.002

Suppose, chemical composition of the compound, temperature and pressure are known. Electronic structure of constituent elements from numerical solution of Quantum chemistry are also known. Then

- There can be only about 230 3D crystallographic lattices. But is there any limit of motif that can be included into the lattice without violating stoichiometry? How ab-initio calculation find out the appropriate motif to put into lattice to generate crystal structure? Without finding motifs, it is impossible to find crystal structures whose Gibbs free energy needs to be minimized.
- Is there any mathematical method that finds out potential energy in an infinite 3D periodic lattice with distributed charges (say, theoretical calculation of Madelung constant)? What are the mathematical requirement/prerequisite to understand such formula?
- How electron cloud density and local potential energy of a molecule/ motif/lattice point can be linked to total Gibbs free energy of molecule/lattice integrated over the whole structure? What are the statistical-mechanical formula that relates the two? and what are the prerequisites to understand such formula?

Suppose reference point for zero gibbs free energy is conveniently provided.

I want to know; What are the tests and conditions that can be performed on a certain equation to say that it represents a good candidate for a multiscale model?

For a complex alloy (suppose Al-Si-Mg-Fe-Cu) , there are multiple linked potential files available in interatomic potential repository, but only a single potential file suffices for implementation of a single-element metal. Can you indicate me clearly how these declarations are done inside LAMMPS script file? Please provide with links to LAMMPS documentation.

I am a materials science undergrad, interested to know the algorithms for numerical integration of equation of motion in computational materials science, like molecular dynamics. It is said that, time-reversal symmetry is essential for such simulations, while classic integration schemes like Trapezoidal, simpsons or weddle methods handle previous and next time step differently. So verlet algorithm is used instead.

Position verlet indeed adds previous and past timesteps and maintains time-reversal symmetry. But velocity verlet doe not. Why is time-reversal symmetry not important for velocity? is it because time reversal symmetry is meaningful only for position and its even derivatives, as in newton's law of motion?

My knowledge on Numerical analysis is only of introductory level, and i have not deeply studied Lagrangian, chaos theory, group theory or hyper-dimensional geometry yet.

Octo-Alloy, also called Ashtadhatu, is a traditional alloy to produce religious idols, ornaments and sculptures in indian subcontinent. My question regarding the alloy is

- According to wikipedia,( https://en.wikipedia.org/wiki/ Ashtadhatu ), the alloy consists of gold, silver, copper, lead, zinc, tin, iron and antimony or mercury .
**Does this alloy consisting of so many dissimilar metals undergo phase separation during casting? Are there any research papers available about microstructure of this alloy, or about phase separation prevention of this alloy?** - Again, some ornaments, especially bangles made of this alloy are made in forms of two interwinning wires of different color. Which metals are incorporated into which wire?
**Where can I get credible Archeometallurgical and contemporary methods of casting (temperature, composition, time)and metalworking ( embossing, scribing) of this alloy?**Was this work of a jeweler, a sculptor or a metallurgist?**Is there any possibility that the alloy is a high-entropy alloy? Have there been any research on molecular dynamics simulation of high entropy alloy of these particular alloying elements?**I have not found any in interatomic potential repository**Had there been any research on***MEDICAL (NOT ASTROLOGICAL)*benefit of using octo-alloy( more specifically its self-disinfecting capability and heavy metal poisoning hazard)?

I need someone who has knowledge in SRIM-TRIM code for irradiation damage assessment to assess my designed code for me.

As a Materials scientist, how much necessary is to know about machine learning and Artificial intelligence in order to work on Computational Materials science? My own Computing skills do not go much beyond microsoft Office, and preliminaries of C, SolidWorks and MATLAB. So where to start? Please include references and links.

If you are just interested in the energy of the system and this system has Fe atoms, will it matter to set the MAGMOM tag? Will it affect the computed energies or affect the convergence speed if set wrongly? Thanks.

I have a structure file. I want to input that structure file and get multiple structure files as output with varying lattice parameters. How can I do that using Atomsk. I want to vary the lattice parameter to be used in a LAMMPS simulation. Atomsk is capable of giving multiple output files with varying lattice parameter by bash scripting. But how can I do the same for complex structures?

As title, just roughly calculation is OK.thanks anyway

Please do not refer to JMatPro. It could not calculate for varying boron concentration in the given range.

Any paper describing the process would also be welcome.

Hi everyone!

I want to show band alignment of a hybrid halide perovskite material with an electron transport material ( Fig: CH

_{3}NH_{3}PBI_{3}and TiO_{2}, respectively). The position of VB edge (-5.4 eV/-7.3 eV) and CB edge (-3.9 eV/ -4.0 eV) can be known experimentally (XPS) in both materials (CH_{3}NH_{3}PBI_{3}/TiO_{2}). But can anyone tell me how can we calculate these values of the positions of VB/CB edges using VASP/WIEN2k?Thank you

Dear respected RG members,

I am doing Mulliken population analysis of Cobalt (Co) doped MgO lattice (rocksalt) using CASTEP code (ultrasoft pseudopotential). I found some strange data as follow:

for

**pure MgO**bond population (Mg-O) =

**- 0.73**for

**(3%) Doped MgO**bond population (Mg-O) =

**- 0.31**bond population (Co-O) =

**0.42****Is the negative value of of Mg-O reliable?,**since negative value indicate antibonding, small value close to zero indicate ionic bonding and large positive value (Co-O) indicate covalent bonding. As we know, MgO has a very strong ionic bond, therefore bond population (Mg-O) must be close to zero. All parameters that I used during optimization are correct. I also did the same calculation using ( norm-conserving ). The obtained data gave almost a good result as suggest by Segall et al. (Mg-O = 0.58) and (Co-O = 0.53).

**Thanks in Advance**

Should I fix the k-point density and then increase the energy cutoff in steps until convergence, or should I fix the energy cutoff and then increase the k-point density in steps?

I am looking for some guidance on using forcite module for mechanical property. I'm creating crystal and when trying to do geometry optimization, selecting Compass, while assigning manually, getting some error. Am I missing something. Can you suggest some example manual for forcite module? Thanks.