Questions tagged [electronic-structure]

For questions concerning electronic structure concepts and calculations.

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Database of surface electronic structure

I'd like to compare my simulation result of a TiO2-110 surface's electronic structure, but all the literature shows too many different results, so I'd like to look for a database for surface ...
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22 views

How to get the right type of bandgap(indirect/direct) in VASP?

I am trying to calculate the band gap type(Direct or Indirect) of TiO2-Rutile, according to the Material Project, rutile is a direct bandgap type semiconductor. The VBM and CBM are both at the Gamma ...
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2answers
637 views

Is there a benchmark paper that takes into account how often each molecule is studied?

There are many benchmark sets in different branches of computational chemistry and physics, that are frequently used to assess the "average error" of a method for a certain property, on a ...
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54 views

What input setting in Quantum ESPRESSO will allow me to calculate the free energy of a solid?

I understand that it's possible to calculate the Gibbs free energy of a system ab initio, see for example: How can we calculate the Gibbs free energy from first principles? I'm wondering how I can do ...
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35 views

Validity of estimating electron relaxation time using the smallest cross section of a structure

I am studying nano-scale constrictions in semiconductor materials. Imagine two nano-particles joined together by a single point of crystalline contact to look like an hour-glass filled with sand. ...
8
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2answers
147 views

Mobility and chemical potential

I have been studying the Boltztrap2 software to calculate the thermoelectric properties of materials. However when following the tutorial given, the Seebeck coefficient is plotted against ...
6
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1answer
95 views

How to rotate of polarizability tensor depending upon the molecular coordinates?

My question is somewhat related to molecular rotation. I have calculated the polarizability tensor of HCHO molecule in PSI4. The output tensor is this, ...
5
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2answers
138 views

How can I get started on DFT?

This question is simply: How can we use DFT in the field of electrochemistry? What are the best resources (Books, reviews, papers, software ...) to learn about using DFT in electrochemistry? ...
5
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2answers
140 views

The format and values provided by Basis Set Exchange

In this question and answers, I found that Basis Set Exchange provides information about the orbitals (e.g., the orbital exponents and contraction coefficients). For example, the following example is ...
6
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1answer
144 views

How to choose the best SIGMA value in VASP?

I am trying to test how to choose the SIGMA value in VASP, so I did a little bit of test. Here is the input file: INCAR ...
6
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0answers
44 views

Compute bulk electrical conducitivity from single-crystal measurements

If I have single-crystal measurements of electrical conductivity along 3D axes (considering for example anisotropic materials), is there any straightforward way to compute the bulk (global) electrical ...
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62 views

What are the electronic steps and ionic steps in VASP?

I am getting confused about what the electronic step and ionic step are in VASP. I used to think that finishing the following loop one time is called an electronic step. but I am not sure how to ...
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4answers
666 views

How can I find the parameters in a basis set?

I have a question about the basis functions of Gaussian. When the basis function is set (e.g., 6-31G), I would like to know the specific value of Gaussian's parameters for each atom. In particular, I ...
5
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1answer
113 views

Unrecognized or duplicated keyword error using ORCA

I wanted to run ORCA 5.0.2 with the following input: ...
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0answers
33 views

Segmentation fault during execution of Orca 4.0.0.1

I would like to use Orca 4.0.0.1 under the following Linux version: ...
7
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1answer
77 views

How does coupled cluster doubles (CCD) compare to MP2?

I have seen an increase in the use of the coupled-cluster doubles (CCD) method recently. CCD uses the exponential ansatz of the coupled cluster equations, but only includes amplitudes to double ...
10
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1answer
110 views

Can electron-phonon coupling be extracted from the dielectric function?

Computationally, there are various ways to calculate the electron-phonon coupling constants as a function of phonon index and momentum. My question is about the reverse process. Let us say that an ...
7
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1answer
44 views

Does PySCF support CAS-SCF calculation?

Does PySCF support CAS-SCF calculations? If not, it is possible to implement it based on their GTO integral library?
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40 views

What are Crystal Electric Field Parameters?

What does the following notation mean? $$A_{20}\left<r^2\right> = -100 \mathrm{K}$$ Where $A_{20}$ is termed a Crystal Electric Field Parameter. I often see this notation when reading papers on ...
10
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1answer
72 views

What is signified by the properties of the electronic band structure?

When considering the band structure of two materials or two structures along a specific k path, what exactly is meant by the gradient and the distance between band lines? Does this show any ...
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118 views

How may I calculate the "effective transfer integral" in free electronic-structure software?

I would like to calculate the following four quantities in a free electronic structure program: \begin{alignat}{2}\tag{1} e_1&=\langle\phi_1|H^{KS}|\phi_1\rangle,\\ e_2&=\langle\phi_2|H^{KS}|\...
3
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1answer
23 views

Question regarding conflicting results of checking the electron-preciseness of isoelectronic species via NBO and EHM calculations

(Cross-posting from Chemistry.SE due to recommendation that this be posted here; see comment section) It is well known that the tert-butyl cation's empty 2p orbital on the central carbon is stabilised ...
12
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1answer
293 views

Comparing GAMESS, OpenMOLCAS and Psi4

Over the years many open-source ab initio packages have been developed and the diversity in subroutines, methods and portability (ability to interface with other software) is quite varied for ...
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2answers
206 views

How can I be sure that I have found the conduction band minimum in DFT?

Let's say I want to find the electronic energy bands from DFT calculations in VASP along a chosen path in the Brillouin zone. Now, I want to make sure I choose a path that captures the conduction band ...
7
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1answer
87 views

Electron interactions between different positions or different orbitals

When I consider the grid positions $r$ in a molecular system, I have a matrix, where each row can be regarded as an N-dimensional vector and each column can be regarded as a G-dimensional vector. In ...
5
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1answer
135 views

Ground State energy trick for many-body electronic structure calculations?

I am an outsider to this field, so I am not sure about the validity of my work below. Let us define the following Hamiltonian from DFT: $$ \tag{1}H_{ij} \psi_{ij} \equiv (-\frac{\hbar^2 \nabla_i^2}{2m}...
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3answers
692 views

Why is it so hard to find the ground state of molecules with d-block or f-block elements?

Based on some of my previous reading and questions that I have asked I am aware that determining the ground state electronic configuration for molecules containing d-block elements theoretically is ...
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61 views

Orbital space clustering [closed]

I am interested in how the orbital space of a system can be partitioned into clusters. I read reading 'Cluster many-body expansion: A many-body expansion of the electron correlation energy about a ...
6
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71 views

How to calculate energy gradient and Hessian with respect to only a few internal coordinates using Gaussian? [closed]

I would like to form the (numerical) gradient and the Hessian of the total electronic energy with respect only to a few internal coordinates (namely, the six intermolecular coordinates of a weakly ...
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2answers
190 views

How to find out the multiplicities of molecules containing d and f block species?

I know that the U atom has four unpaired electrons. Therefore it has a total spin S of 2. This means its multiplicity is 2S+1 = 5. Now consider a complicated molecule such as $UF_6$. In theory all I ...
12
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2answers
338 views

For DFT and Hartree-Fock, how can we know that we have a true minimum? Is there an equivalent to the "frequency analysis" for geometry optimization?

In a geometry optimisation, one can check if they have reached a minimum by checking the phonons. And to a certain extent, the global minimum can be confirmed by relaxing from different starting ...
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1answer
71 views

Accurate electron-hole localization for charge-transfer transitions

I'm studying the nature of electronic excitation in conjugated organic dyes. To define the donor and acceptor part I've run TDDFT and CIS calculation, they both gave similar set of configurations for ...
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0answers
43 views

DFT Vasp calculation not converging when doing a SCF calculation for monolayer MoS2 [closed]

I am trying to calculate the electronic structure of Monolayer Molybdenum Disulfide ($\ce{MoS_2}$) using Vasp. However, I encounter problems with convergence. It does not seem that my calculations ...
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2answers
62 views

Are there efficient open source implementations of electrostatic potential integrals?

We've had several questions regarding calculation and plotting of electron density. The electrostatic potential represents the interaction between a point charge at a given point $\mathbf{r}$ in a ...
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1answer
196 views

Visualize electron density using pyscf

I found the following example of code which uses density functional theory to compute the electron density $\rho$: ...
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2answers
113 views

Can the color of gold metal be reproduced by modeling only the conduction electron band structure, or do atomic absorption lines contribute?

@JohnCuster's answer to Why is gold golden? is based on the band structure of the delocalized conduction electrons in gold, whereas other answers there tend to support the "Gold is gold due to ...
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1answer
106 views

Computing analytic derivatives of molecular Hamiltonians obtained from solving Hartree-Fock equations

I'm currently working on a quantum chemistry project, I am dealing with a second-quantized electronic Hamiltonian (corresponding to some molecule), written in terms of fermionic creation and ...
5
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1answer
103 views

Calculating first and second derivatives of a molecular Hamiltonian?

I'm interested in computing first and second derivatives of molecular Hamiltonians with respect to nuclear coordinates. I've been using Psi4 and PySCF to perform Hartree-Fock calculations, and I was ...
8
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1answer
174 views

Error while doing a band structure calculation in Quantum ESPRESSO

I have been using BURAI GUI of Quantum ESPRESSO to calculate the optical properties of ZnSe quantum dots. But first I wanted to calculate the electronic band structure. After running the calculation ...
11
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1answer
356 views

Increasing k-point grid to take DOS calculation

I was trying to compute some electronic properties for Pd using SIESTA and VASP for some computer practicals in my university, specially focused on band structure and density of states (DOS) using LDA ...
9
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1answer
151 views

What is the electrical behavior of the material with this band gap?

Presently I am doing DFT calculations to analyse the electronic structure of a material. I got the band structure as shown in the figure. I would like to know the electrical behavior of this material. ...
6
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86 views

Calculating excited states using GAMESS CISD module [closed]

I am trying to compare the energies of the excited states of $\ce{C12H9N}$ molecule using the CIS and CISD module implemented in the quantum chemistry package in GAMESS. While I can easily obtain the ...
6
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1answer
332 views

VASP error when trying to do calculations in the presence of an electric field

I am trying to observe the effect of the electric field on 2D materials. I applied electric field by introducing three tags: ...
12
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1answer
202 views

How does one project out the translations and rotations from a Hessian?

I've recently written a simple code to numerically compute the Hessian of some function (at a point). Most electronic structure packages will compute the Hessian and then project out the translations ...
12
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2answers
87 views

What are some of the advantages and disadvantages when using shape consistent pseudopotentials as compared to energy consistent pseduopotentials

From the literature as well as the answer to the question What is the meaning of energy-consistent and shape-consistent in the context of pseudopotentials? I can see that the key difference between ...
13
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1answer
127 views

What is a good practical way to determine whether or not I need to use a multiconfigurational method?

I’m planning to run a calculation of single electron transfer where my system goes from singlet to triplet biradical (presumably). So I’m wondering how to decide if I need to use milticonfigurational ...
14
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1answer
493 views

Gaussian-type orbitals vs Slater-type orbitals in terms of computational efficiency

When creating molecular orbitals via the linear combination of atomic orbitals method I am told that Slater orbitals provide a more accurate representation whilst Gaussian orbitals are computationally ...
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83 views

Calculating single electron transfer

I'm thinking about doing some computational research about pyrazoline oxidation in chlorinated solvents under light. I've found plausible mechanism (article) that involves single electron transfer ...
9
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1answer
196 views

PT-symmetry leading to spin-degenerate band structures

I am trying to understand the fundamental physics of a kind of problem. I will introduce a specific example and then list some of the broader qualms I hold. I have observed many band structures, be it ...
7
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1answer
114 views

What differences are there when modeling metal-organic-frameworks as isolated clusters or periodic solids?

Should I take MOF (metal-organic framework) as a periodic structure or an isolated cluster? What's the difference between them? If it's periodic, can I do an analysis of the electronic structure, such ...