Electronic Structure - Science topic

For the calculation of the total energy in VASP, it is recommended to use tetrahedron method with Blöchl corrections (ISMEAR=-5). And for 2D slabs in the z direction (perpendicular to the surface), it is recommended to give only 1 k point since there is vacuum above surface (The middle layers we freeze the atoms).

But when ISMEAR=-5 is used in VASP, an error comes

Tetrahedron method fails for NKPT<4. NKPT = 3

So should we use Methfessel paxton/Gaussian smearing in this case?

I heard that the electronic structure of the precursor is changed and the valence state difference occurs due to metal ion doping, so I wonder how this improves structural stability.

It is commonly believed that the concept of electron spin was first introduced by A.H. Compton (1920) when he studied magnetism. "May I then conclude that the electron itself, spinning like a tiny gyroscope, is probably the ultimate magnetic particle?"[1][2]; Uhlenbeck and Goudsmit (1926) thought so too [4], but did not know it at the time of their first paper (1925) [3]. However, Thomas (1927) considered Abraham (1903) as the first to propose the concept of spinning electron [5]. Compton did not mention Abraham in his paper "The magnetic electron" [2], probably because Abraham did not talk about the relationship between spin and magnetism [0]. In fact, it is Abraham's spin calculations that Uhlenbeck cites in his paper [4].

Gerlach, W. and O. Stern (1921-1922) did the famous experiment* on the existence of spin magnetic moments of electrons (even though this was not realized at the time [6]) and published several articles on it [7].

Pauli (1925) proposed the existence of a possible " two-valuedness " property of the electron [8], implying the spin property; Kronig (1925) proposed the concept of the spin of the electron to explain the magnetic moment before Uhlenbeck, G. E. and S. Goudsmit, which was strongly rejected by Pauli [9]. Uhlenbeck, G. E. and S. Goudsmit (1925) formally proposed the concept of spin[3], and after the English version was published[4], Kronig (1926), under the same title and in the same journals, questioned whether the speed of rotation of an electron with internal structure is superluminal**[10]. Later came the Thomas paper giving a beautiful explanation of the factor of 2 for spin-orbit coupling[11]. Since then, physics has considered spin as an intrinsic property that can be used to explain the anomalous Seeman effect.

The current state of physics is in many ways the situation: "When we do something in physics, after a while, there is a tendency to forget the overall meaning of what we are working on. The long range perspective fades into the background, and we may become blind to important a priori questions."[11]. With this in mind, C. N. Yang briefly reviewed how spin became a part of physics. For spin, he summarized several important issues: The concept of spin is both an intriguing and extremely difficult one. Fundamentally it is related to three aspects of physics. The first is the classical concept of rotation; the second is the quantization of angular momentum; the third is special relativity. All of these played essential roles in the early understanding of the concept of spin, but that was not so clearly appreciated at the time [11].

Speaking about the understanding of spin, Thomas said [5]: "I think we must look towards the general relativity theory for an adequate solution of the problem of the "structure of the electron" ; if indeed this phrase has any meaning at all and if it can be possible to do more than to say how an electron behaves in an external field. Yang said too: "And most important, we do not yet have a general relativistic theory of the spinning electron. I for one suspect that the spin and general relativity are deeply entangled in a subtle way that we do not now understand [11]. I believe that all unified theories must take this into account.

What exactly is spin, F. J. Belinfante argued that it is a circular energy flow [12][15] and that spin is related to the structure of the internal wave field of the electron. A comparison between calculations of angular momentum in the Dirac and electromagnetic fields shows that the spin of the electron is entirely analogous to the angular momentum carried by a classical circularly polarized wave [13]. The electron is a photon with toroidal topology [16]. At the earliest, A. Lorentz also used to think so based on experimental analysis. etc.

1) Is the spin of an electron really spin? If spin has classical meaning, what should be rotating and obeying the Special Relativity?

2) What should be the structure of the electron that can cause spin quantization and can be not proportional to charge and mass?

3) If spin must be associated with General Relativity, must we consider the relationship between the energy flow of the spin and the gravitational field energy?

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* It is an unexpectedly interesting story about how their experimental results were found. See the literature [17].

** Such a situation occurs many times in the history of physics, where the questioned and doubted papers are published in the same journal under the same title. For example, the debate between Einstein and Bohr, the EPR papers [18] and [19], the debate between Wilson and Saha on magnetic monopoles [20] and [21], etc.

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Reference：

[0] Abraham, M. (1902). "Principles of the Dynamics of the Electron (Translated by D. H. Delphenich)." Physikalische Zeitschrift 4(1b): 57-62.

[1] Compton, A. H. and O. Rognley (1920). "Is the Atom the Ultimate Magnetic Particle?" Physical Review 16(5): 464-476.

[2] Compton, A. H. (1921). "The magnetic electron." Journal of the Franklin Institute 192(2): 145-155.

[3] Uhlenbeck, G. E., and Samuel Goudsmit. (1925). "Ersetzung der Hypothese vom unmechanischen Zwang durch eine Forderung bezüglich des inneren Verhaltens jedes einzelnen Elektrons." Die Naturwissenschaften 13.47 (1925): 953-954.

[4] Uhlenbeck, G. E. and S. Goudsmit (1926). "Spinning Electrons and the Structure of Spectra." Nature 117(2938): 264-265.

[5] Thomas, L. H. (1927). "The kinematics of an electron with an axis." The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science 3(13): 1-22.

[6] Schmidt-Böcking, H., L. Schmidt, H. J. Lüdde, W. Trageser, A. Templeton and T. Sauer (2016). "The Stern-Gerlach experiment revisited." The European Physical Journal H 41(4): 327-364.

[7] Gerlach, W. and O. Stern. (1922). "Der experimentelle Nachweis der Richtungsquantelung im Magnetfeld. " Zeitschrift f¨ur Physik 9: 349-352.

[8] Pauli, W. (1925). "Über den Einfluß der Geschwindigkeitsabhängigkeit der Elektronenmasse auf den Zeemaneffekt." Zeitschrift für Physik 31(1): 373-385.

[9] Stöhr, J. and H. C. Siegmann (2006). "Magnetism"(磁学), 高等教育出版社.

[10] Kronig, R. D. L. (1926). "Spinning Electrons and the Structure of Spectra." Nature 117(2946): 550-550.

[11] Yang, C. N. (1983). "The spin". AIP Conference Proceedings, American Institute of Physics.

[12] Belinfante, F. J. (1940). "On the current and the density of the electric charge, the energy, the linear momentum and the angular momentum of arbitrary fields." Physica 7(5): 449-474.

[13] Ohanian, H. C. (1986). "What is spin?" American Journal of Physics 54(6): 500-505. 电子的自旋与内部波场结构有关。

[14] Parson, A. L. (1915). Smithsonian Misc. Collections.

[15] Pavšič, M., E. Recami, W. A. Rodrigues, G. D. Maccarrone, F. Raciti and G. Salesi (1993). "Spin and electron structure." Physics Letters B 318(3): 481-488.

[16] Williamson, J. and M. Van der Mark (1997). Is the electron a photon with toroidal topology. Annales de la Fondation Louis de Broglie, Fondation Louis de Broglie.

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[17] Friedrich, B. and D. Herschbach (2003). "Stern and Gerlach: How a bad cigar helped reorient atomic physics." Physics Today 56(12): 53-59.

[18] Bohr, N. (1935). "Can quantum-mechanical description of physical reality be considered complete?" Physical review 48(8): 696.

[19] Einstein, A., B. Podolsky and N. Rosen (1935). "Can quantum-mechanical description of physical reality be considered complete?" Physical review 47(10): 777.

[20] Wilson, H. (1949). "Note on Dirac's theory of magnetic poles." Physical Review 75(2): 309.

[21] Saha, M. (1949). "Note on Dirac's theory of magnetic poles." Physical Review 75(12): 1968.

Density functional theory (DFT) gives the ground state electronic structure of a system (material). There are packages like QUANTUM ESPRESSO, VASP, etc., that calculates the electronic structure based on the DFT. I am wondering if it is possible to calculate the electronic band structure at a particular temperature in these codes so that the evolution of the band structure with temperature can be seen?

Any kind of help is highly appreciated.

Thank you !

Can someone provide or give me an example how the VASP WAVEDER file looks like?

Quantum Espresso is a popular open-source software package for quantum simulations of materials. It is widely used by researchers in material science to study the electronic, structural, and thermodynamic properties of materials. In this review, we will discuss some recent research works that have successfully utilized Quantum Espresso to solve complex material science problems. We will also discuss the limitations of the software package and potential avenues for future research in this field.

in terms of electron structure and orbital hybridization

In the Moller-Plesset Perturbation Theory, the second order correction to the ground state energy can be divided into a same-spin and an opposite-spin terms by integrating the spin out. This allows to get integrals using only space orbitals, just as specified on the psi4 website here: https://psicode.org/psi4manual/master/dfmp2.html

I was able to get the expresion for opposite spins. However, when trying to perform the integration for same spins, I haven't been able to get rid of one of the terms and get the expresion I want. This happens because all four orbitals have the same spin function, so every term should mantain after the integration.

What specifications of laptop arerequired to run long electronic structure and optical properties calculations i.e., hybrid functional methods. Kindly share experience.

I am quite new to quantum chemistry calculations and I am trying to calculate the electronic structure of a single 102 atom organic molecule using ORCA software dft functionality. For other codes such as VASP and quantum espresso there is a k points directive that specifies the bloch vectors for band structure calculations of periodic structures. If I just put the geometry optimized single molecule structure to ORCA with B3LYP hybrid GGA, I get the required data, but I don't know if I am doing something wrong. Do I need to specify somewhere in the input file that my molecule is not periodic?

Hello all, I'm attempting to analyze the effect of defects on the electronic structure by adding them into a 4x4x4 supercell and looking at the band diagrams. I've only done band calculations for unit cells before and so wanted to clarify a couple of things. I know introducing the defects will break my symmetry (cubic) but I thought that it will still be 'near cubic' symmetry and that I could still treat it as cubic and get meaningful information by looking at those lines of symmetry (gamma to X, X to M, M to Gamma, Gamma to R, R to X and R to M). I expected to see 4x repeats along each line of symmetry due to using the supercell instead of the unit cell, but that's not what I got. Also I'm realizing that since I have an even number of super cells 0.5 0.5 0.5 is not the same point as it would be for a unit cell. Does anyone have a source for how to address this or do I just need to go through all of the geometry shifting in K Space manually? I found a couple of old links but they're all broken.

I know that at nanoscale conductance is quantized and is determined by transmission probability and number of transmission channels (G value). I know that using uncertainty principle we can derive how I/V becomes 2e^2/h. However, I am a little confused by the zero bias and finite bias conductance. Does zero bias conductance mean that even if we do not apply any voltage, current would still flow?

Dear all, I am studying electronic structure of quantum dots using castep. And I would like to passivate the dangling bonds with hydrogen atoms, but as mentioned in the attached papers,there are two kinds of hydrogen atoms,real one and pseudo one.I think the usual way in castep is using real hydrogen atoms. And I would like to know whether we can use pseudo one in castep?

Could someone help me, I have a cif file and I want to perform electronic structure calculations in abinit or qe, however, when viewing the cif file, it presents several identical structures spliced together, and with many hydrogen atoms (I'm not sure if it's hydrogen), Could someone help me or guide me on how to clearly see that structure. Thanks in advance

How the electronic structure (band structure) affects the thermo-electric properties of a material? or effect of band structure on thermoelectric properties of material?

Hello everyone.

I was wondering if there is litterature that study the influence of the hydrostatic pressure on the electronic band structure from a theoretical point of view. I've found many papers that shows the evolution of the band gap and the electronic structure with the pressure but not one with a theoretical study of that.

Best wishes.

Benjamin Martin.

Hello everybody. I want to simulate the effect of Ag on the structure and electronic properties of CdTe. For this, I chose the cubic structure of CdTe and calculated the electronic properties in the Wien2k package. The band gap obtained is 1.51 eV (mBJ), which is in agreement with experiment. Then I replaced one Ag atom with Cd in the CdTe supercell with a size of 2 * 2 * 2. After optimization, I repeated the calculations, but at the same time I got a band gap of 0 eV. I thought that the problem was in optimization through Wien2k and decided to ask a friend from Russia for help to optimize the system on VASP, but after optimization on VASP nothing changed.

Please help me to properly optimize the structure and simulate the effect of Ag on the electronic structure of CdTe.

Thank you in advance

I am trying to learn Gaussian using the book Exploring Chemistry with Electronic Structure Methods. The book suggests using APFD model but every time I use it, an error appears (see below)

Server Error #2070

The processing of the last link ended abnormally.

All processing has been aborted.

I am still new to this, so troubleshooting is very difficult. Please help!

I am currently running some QTAIM topology analyses of main group compounds to elucidate their electronic structures. In particular I would like to use delocalisation indices (DI) to quantify the amount of single- or double bond character in these species. The situation is complicated by the presence of non-nuclear attractors at the centre some of the bonds, preventing a direct interpretation of DI values. It seems possible to calculate an "effective" delocalisation index for the two atoms that are bonded but have a NNA located between them.

I read a footnote in a paper (Chesnut, Heteroatom Chemistry 2002, 13, 53) that mentions

"A non-nuclear attractor (NNA) is found in the Si Si bond midpoint in this molecule. An effective Si Si delocalization index is determined by presuming that half of the NNA belongs to each silicon atom. This removes the NNA from the picture while preserving the sum of the Fii and Fij terms."

I am a bit stuck at the moment, trying to reproduce the numbers for some of the compounds from the referenced paper. Has anyone experience with such situations and would be able to provide some more detail or a protocol on how to exactly obtain these effective DIs?

I'd appreciate any input. Thanks in advance.

Kind regards,

Tobias

Dear Colleagues,

I want to calculate the Electronic structure distribution and the structure of Simple molecules like H2 , H2O and NH3.

I want to calculate by first principle approach.

Please suggest me which process should I use for this.

Thanks and Regards

N Das

i am using quantum espeesso and need to understand what is k-space and how to set it.

We know that the density functional theory (DFT) is nicely applicable for finding the material's electronic structure and related properties.

Is it possible to find the optical properties as well? If possible then please help me by sharing some well-written examples.

Thanks in advance.

It is know that XPS (X-ray Photoelectron Spectroscopy) gives elemental composition (what elements are present) and the chemical state/s (what other elements they are bonded to). I wish to know how XPS helps in knowing overall ''electronic structure'' and ''density of electronic states'' in the material being characterized.

Hello,

I am a newbie in theoretical solid-state physics. I am now trying to calculate

electronic energy-band structures using Quantum ESPRESSO solver.

The relevant cell (lattice) has following conditions;

1. This unit cell is described by three lattice vectors

1. They are, v1=(-0.5,0.5,0.0), v2=(0,1,-1), v3=(-0.5,0.5,1.0)

1. vectors are normalized with a-lattice length

1. This unit cell has eight-atoms

1. four cations (C) and four anions (A)

1. The system has effective cubic symmetry

Based on these conditions, I wrote a part of input file as below. C and A respectively

stand for cation and anion. I thought that the atoms should be just allotted

on apexes (vertices) of a cube. I wonder this Is correct?

Thanks for any advices. Answers using cif or VASP Poscar formats are also

very welcome so that they can be converted with cif2cell or Vesta.

CELL_PARAMETERS -0.5 0.5 0.0 0.0 1.0 -1.0 0.5 0.5 1.0 ATOMIC_POSITIONS C 0 0 0 C 1 1 0 C 0 1 1 C 1 0 1 A 1 0 0 A 1 1 1 A 0 0 1 A 0 1 0

Dear all,

We came across an organic compound that shows possibly a very large Stokes shift and wonder what is the largest number in eV ever reported. Any suggestion from the experts?

Thanks for your help!

Keisuke

We all know that when solving the wave function of an electron, both the initial and boundary conditions can influence the energy state structure of the electron. We also know that the boundary condition is somehow determined by the particle size and its surface. So, how does the atomic structure of surface finally affect the electronic structure of a nanoparticle? Are there some specific examples to explain it?

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

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?

See some of my related questions

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

(The image is taken from wikipedia https://en.wikipedia.org/wiki/Periodic_table_(crystal_structure) ,

and I claim no originality of creating the image)

The reason of the following structures are given in wikipedia, with some exceptions, at room temperature.

If all of these can be explained in terms of electronic configuration , then a significant electronic-to-crystal structure interrelation in simpler terms can be obtained.

(and possibly, ratio of metallic bandgap or Fermi energy etc. like energy parameters and average electron K.E at room temperature, then I think the correlation would be stronger. Perhaps, if one replaces spherical model of a metallic atom with its feasible 3D dirctional variation of outermost electron shell geometry, the the correlation is likely to be even stronger)

It is hypothesized that the nature/energies/electron distribution of the frontier orbitals of a molecule changes under external field condition. Under applied bias, the molecule can be oxidised/reduced and this changes its electronic distribution and eventually the molecules ability to conduct current. Can we model such an hypothesis using DFT in Turbomole? Some information in this regard is very welcome.

Dear Respected Colleagues,

We know Ground state Hydrogen Atom has it's Electronic structure as a spherically symmetric distribution and radially varies as given by 1S wave function.

I want to find the change of electronic structure distribution when two Hydrogen Atoms are taken closer and closer and form a stable Hydrogen Molecule.

Please suggest any method of solving this problem.

Thanks and Regards

N Das

Hi everybody, I am a new user wien2k 14. I am trying to optimize the electronic structure of ternary alloy (with 8 atom in the unit cell) but I am not sure about the good k points number.

Thank you.

In most electronic structures the fermi level is always shifted to zero , why ?

Regarding electronic structure is there any relation to reduction of lattice constants and GGA approach?

I have prepared CeO2 based nano-particles. due to some technical issues some of the properties like electronic structure and magnetic properties are pending. the samples were prepared approximately 6-7 months before. Since nanoparticles have a tendency to agglomerate then for further characterization, may I have to anneal them again?

Dear All

As I am new to research (study of Heusler alloys using DFT) ,I am trying to reproduce the results of the problems already published in research papers. I am currently working on the Heusler Alloy Co2MnSi and trying to find its electronic structure and magnetic properties etc.using Quantum espresso. I have been using different paseudopotentials (Ultasoft as well as Norm conserving) but not getting the lattice parameter correct. Although the magnetic moment is coming out to be accurate. So my question is how one decide which pseudopotential is to be used in a particular problem? And suppose we do not know the experimental values as say it is some novel material which has not been under the experimental lens; then how one go about in choosing a pseudopotential in such a case?

To describe optical properties how can we make relation with electronic structure? Can any one provide a good reference?

I know we can edit the layers (and make different cifs) and do the calculation for each layer separately to find their HOMO-LUMO. But I was wondering if there's a way to calculate HOMO-LUMO of each layer, while the layers are stacked in the heterostructure in a single cif. Thanks!

*I'm using Quantum Espresso. But I guess the problem is same the regardless of the code one is using.

I'm new to electronic structure calculations. I have been doing some band structure calculations. I am seeing some crossing in the band structure, a pair of crossing actually. I plotted the S{z} component resolved bands also. The points seem to be of same sign of S{z}. So, how do I make sure that a crossing is Weyl point or something else?

P.S. I have done the SOC calculations. Attaching the picture. Look around -0.05meV.

Do we have a number for DOS (Nv, Nc) for 3D or 2D perovskites? Although I see few papers reporting DOS, I do not find a number. Or maybe I do not find a way to calculate DOS from the plots.

I've tried to find proper answers for it but cannot find one.

1. So the question is that is it possible or reliable to apply external electric field on 3D system in VASP?

There are some works on 2D system with external electric field like graphene, but it seems like there's nothing regarding 3D system.

I found that EFIELD, LDIPOL, IDIPOL, EFIELD_PEAD are key tags to apply external electric field.

However, in the web ( https://www.vasp.at/wiki/index.php/EFIELD ) it states only about slab or molecule model.

Also, EFIELD_PEAD looks like it has no effect on geometry

( https://www.vasp.at/forum/viewtopic.php?t=17390&p=18296 ), only affects to electronic structure.

2. The second question here is that do the other three tags(EFIELD, LDIPOL, IDIPOL) also give changes to electronic structure only or geometrical change also?

Thank you

In general the low loss electron energy loss peak contain the information about the electronic structure of materials. From free electron model (Drude Model) the plasmon energy is given by a relation

E_p = sqrt. (ne²h²/ π m)

where,

n = conduction/valence electron density

e= electron (hole) charge

m= electron (hole) effective mass

h= Plank's constant

Once we have "n" values we can calculate Fermi wave vector and followed by Fermi energy. My concern is that, is it applicable for compound like Ni₃Al, Ni₃Nb and Fe₃C, so on, or it is only applicable for solid solution alloys.

Thanks

PS M Jena

I am doing research on modifying the bandgap of materials. I would like to know computationally the changes in the electronic structures of the host material with any modification like doping. I want to learn the computational methods available like DFT to calculate the electronic structures. Please suggest some reliable sources from where I can start learning this type of calculations.

Thanks

I want to know where to find the details of calculating electronic structure of a solid state material using DFT in Quantum Espresso. Any reference or site where I can learn this?

I want a detailed lesson on it.

Hi, I can not optimize a palladium (II) coordination complex in Gaussian 09W, the calculation ends with an error. Should I treat the wave function as an open shell or as a closed shell? Thank you

Hi all.

Although very trendy nowadays, Can DOS for a single molecule provide us any useful information about the electronic structure of that species in bulk.? If yes, can you give some references?

I am doing this calculation using Gaussian 09 on a planar sheet.

Thank you

My system has inversion symmetry. Therefore, I'm calculating the optical transition for a material which is allowed when parities of conduction band (CB) and valence band (VB) are different (there is some finite probability for it), otherwise it is zero. I have obtained the WAVEDERF file that contains some band number (occupied and unoccupied) with specific energy, and real and imaginary part of dipole transition matrix elements. I want to plot (K-path/K-points vs. optical transition probability), but do not know how to obtain this from WAVEDERF file.

Any help would be appreciated.

How entering of triiodide ion into starch coils change electronic structure of iodine? iodine is post-transitional element, so , can ligand field theory be applied here? How the electronic transition of outermost p orbital produce visible color?

Please explain in simple terms, since my knowledge on electronic structure of complex ions , macromolecular ligands, ligand field theory and quantum chemistry are rather limited.

I have a electronic structure (band-structure calculated using VASP), which contains \Gamma_{8}, \Gamma_{7}, \Gamma_{6} bands theoretically. Now, my question is, how can I identify and find out exact position of these bands with respect to band energy ?

Thanks,

I have tried the command: 

%output 

pdbfile pdbfile

end

but its doesn't work. Any suggestions or sample input files? 

I have done anharmonic frequency calculations in Gaussian09.(for acetone). At the end of the output file I can see the anharmonic frequencies. I do not see anharmonicity constant value(for different vibrational modes) though. Can we get anharmonicity constant value?

Also, I want to know how are anharmonic frequencies calculated? What theory is encoded within Gaussian software to calculate these values? How reliable are those?

Any reference paper will help.

Thank you.

hello dear researchers

i want to calculate electron affinity in quantum espresso code but i dont know how to do it. i red in a link that electron affinity calculation, related to delta scf calculation in DFT method but i dont know it. can you guide me about this?

thanks a lot

Hello

I am a graduate student studying the electronic structure of penta-silicene bilayer. I want to know how to calculate the formation energy of penta-silicene bilayer. Can somebody give me some infomation about it?

thank you for taking time reading and answering my question

I can see a lot of information for one specific space group on the 'international table of crystallography'. Say I know the space group of a crystal from XRD analysis, and I want to calculate electronic structure using first principle; but, I would need the positions of the atoms as well which I don't find what and how the authors put in their papers. So, I would be very grateful if someone who is much familiar with the 'international table of crystallography' or the Wyckoff things can help me. Thanks in advance!

I'm studying about 2D material-penta silicene to accomplishment of graduate thesis. After a few steps of calculation, i realized it was wrong about position of atom in unit cell so can somebody give me some advise to do better ?

Thank all of you.

Is there a way, to get the same electronic structure of the Bilayer graphene and isolated monolayer graphene?

I performed relax calculations for MgO supercell with an Fe interstitial atom. The CONTCAR file which contains the final atomic positions indicate that only Mg and O atoms have moved with Fe being in the same initial position as given in the POSCAR file. It is quite strange that a single Fe atom in a big Mg32O32 supercell is able to distort the other atoms with itself not moving. PFA all the related files.

I found some guys publish their papers in high impact journals for photocatalysis and catalysis.

For example, a guy presented a calculation of the barrier of a catalytic activity on 1T MoS2 surface by considering only its monolayer. This is entirely incorrect. There are two reasons.

(1) 1T is much less stable than 1T' phase. (2) 1T' phase is only stable when some kinds of chemical species are intercalated to make significant charge transfer to MoS2. The charge transfer introduces significant effect on the electronic structure of MoS2. Their calculation should be redone from the beginning.

Chemical society should be more careful in undertstanding basic physics underlying the catalytic activity. Chemistry should not exclude physics.

As per "Exploring Chemistry with Electronic Structure Methods" 3rd Edition book, R.E.D tool are used to calculate MM charges http://upjv.q4md-forcefieldtools.org/RED/

However the download link is not working.

1) Do you recommend other downloadable sotware compatible with windows?

2) Do you recommend other tutorials to follow to perform ONIOM job ?

BTW, I am using Gaussian 09 on supercomputer (Linux shell) and gaussiaview installed on my windows PC.

I need to conduct some research on TiO2! I could use some help!

I am studying electronic structural features of 2D materials which contain almost more than 30-40 atoms in the unit cell. I think it is more tedious writing direct python scripts like for a 2 atom unit cell material. Can anyone please suggest me to succeed in this case?

I am working on the organic-inorganic complex of Sn2+. I am trying to stabilize sn2+ by compelexing it with some organic molecules. How can I explain this stability is related to changing of electronic structure of Sn2+ by XPS and UPS. Is it possible to talk about electron affinity of Sn2+ by these two method?

Thank you in advance

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?

First principle simulation of Semiconducting nanomaterials with VASP.

Dear all,

I want to calculate the band diagram of perovskite, for example: tetragonal crystal structure with some organic molecule on the edges or in center.

To do that I need to choose k-point path. It's quite difficult to choose them wisely for casual crystal cases, without molecules inside. What with the crystal cells containing molecules. If I obtain the the way of making Wigner-Seitz cell ( pl.wikipedia.org/wiki/Kom%C3%B3rka_Wignera-Seitza#/media/File:Bcc-animated.gif ) I can see that the edges of this cell in reciprocal space set the Brillouin zone (I think it's a definition), everything is okay with that for me untill I add a molecules on the unit cell edges or in the center. I belive it's gonna change the shape of the Wigner-Seitz cell of the same e.g. tetragonal structure without molecules.

Is it approximation when people in papers said that their perovskite is e.g. tetragonal and they set k-point path through the high symmetry lines and points like for simple tetragonal phase ( like for example here: en.wikipedia.org/wiki/Brillouin_zone#/media/File:Simple_Orthorhombic_Lattice_(Brillouin_zone).png )? If it is approximation what is the cost, limits etc.

I want to find the conical intersection for H2S molecule in the first two excited states.

What all information is required to make the input ?

Dear all,

we are doing phonon DFPT calculations with vasp and we are using the following input:

#################

PREC = high

ISMEAR = 0

ISPIN = 2

ENCUT = 550

SIGMA = 0.05

EDIFF = 0.00000001

EDIFFG = -0.01

IBRION = 8

NSW = 1

LCHARG = .FALSE.

LWAVE = .FALSE.

LREAL = .FALSE.

ADDGRID = .TRUE.

IALGO = 38

#################

To my understanding, the electronic structure calculation should be considered as converged, when the energy difference between two scf cycles is less than the value specified under EDIFF.

However, if I look into the OSZICAR file (attached), I see for the first step that 60 scf cycles has been done, which is also default setting for the maximum number of scf cycles per ionic step. In the OUTCAR file, I also find the line with "aborting loop because EDIFF is reached" after the 60 cycles. 

What I don't understand here is that the difference between two scf steps is already smaller than EDIFF after 35 scf cycles. So does anybody know, why vasp is not considering the electronic structure as converged after 35 steps? Is there any additional convergence criteria other than EDIFF when using IBRION=8?

We are using VASP.5.2.11.

Best wishes,

Cheng-chau

I am interested in knowing what the physical interpretation of NBO analysis is. I have done NBO calculation for some molecules using GAMESS code. How can NBO explain the stability of molecules?

I know how to calculate the excited electronic states, but it is not enough to determine the maximum absorption. I also need excited vibrational energies.

How can I acquire these results?

In the hypothetical case of a system that may require crossing between manifolds of different multiplicities:

Two PESs are created for a heavy atom abstracting a hydrogen atom. One is the triplet PES and the other is the singlet PES. Ground state singlet-triplet gaps are non-trivial.

The triplet TS is lower in energy, but at some point in the reaction coordinate, the singlet reaction path becomes energetically favorable. The experimentally observed product is in the singlet state. Where does the system undergo inter-system crossing (ICS) to arrive at the product? At the crossing point or at the product? How does ICS figure into kinetics? How does one describe kinetics if this point of intersection is before the TS? Is there a name for these kinds of scenarios?

In the electronic configuration of transition metal we first fill 4s-orbital since the energy of 4s-orbital is less than the 3d-orbital due to screening of nucleus charges. But when the 3d-orbital is filled up with electron after having been filled up 4s-orbital, the energy of 3d orbital is found to be reduced. What is the reason behind it?