Questions tagged [electronic-structure]

For questions concerning electronic structure concepts and calculations.

Filter by
Sorted by
Tagged with
6 votes
1 answer
191 views

Meaning of Kronecker Product in Transport Theory behind BoltzTrap2

I am somewhat confused by the use of a Kronecker Product in Madsen, Georg K. H. et al. “BoltzTraP2, a program for interpolating band structures and calculating semi-classical transport coefficients.” ...
user avatar
  • 584
5 votes
1 answer
59 views

Are multiplet free atoms multireference?

In general, my understanding is that free radicals and non-equilibrium molecules sometimes need multireference electronic structure calculations, mainly because of different electronic states being ...
user avatar
14 votes
2 answers
232 views

Textbooks for electronic structure theory

Through this post I am looking to create a resourceful list of textbooks for any one interested in electronic structure theory. The focus here is to create mostly a mutually exclusive list of answers ...
user avatar
4 votes
0 answers
86 views

electronic structure of (110) Nb

I need to get the optimal number of layers of (110) niobium that is a good representative of the behavior of the material, but I am facing two problems using Quantum Espresso, I Keep getting the ...
user avatar
  • 151
7 votes
1 answer
91 views

Fitting GTOs to other density/wavefunction representations - state of the art?

When using most molecular electron structure codes that use GTOs for the density or wavefunction, it is possible to project the first-order density matrix onto 'natural orbitals' with MOs expressed ...
user avatar
  • 361
10 votes
2 answers
302 views

FCI without Hartree-Fock

Recently, I came across some lecture notes on electronic structure theory which had something peculiar about it. I noticed that FCI (configuration interaction) was introduced before Hartree-Fock ...
user avatar
9 votes
2 answers
263 views

Numerically integrating the Hartree potential

I'm trying to write a 1D density functional theory code on Python to predict the electronic structure of certain ions using the local density approximation. I'm trying to construct the hamiltonian for ...
user avatar
6 votes
1 answer
123 views

Is it possible to calculate the dipole polarizability in the presence of a nonzero electric field?

One common way of calculating a dipole polarizability from electronic structure is by calculating the following derivative by finite difference: $$ \mathbf{\mu}=\left(\frac{\partial U}{\partial \...
user avatar
  • 2,461
5 votes
0 answers
58 views

Cheap NMR shift calculations in periodic systems

I am looking for an electronic structure method code (e.g. tight binding DFTB) that supports cheap calculations of NMR shieldings and has support for periodical systems. I would be grateful for any ...
user avatar
5 votes
1 answer
187 views

Do the U values affect structure optimization with the DFT+U simulation to optimize crystal structure?

I am trying to do structure optimization of TiO2, since titanium is a transition metal, I need to use DFT+U to simulate the right band structure, but the electronic band structure would also affect ...
user avatar
  • 1,601
2 votes
0 answers
51 views

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 ...
user avatar
  • 1,601
5 votes
0 answers
110 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 ...
user avatar
  • 1,601
8 votes
2 answers
659 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 ...
user avatar
  • 6,643
3 votes
0 answers
137 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 ...
user avatar
  • 3,599
5 votes
0 answers
63 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. ...
user avatar
  • 2,454
8 votes
2 answers
227 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 ...
user avatar
7 votes
2 answers
182 views

How to rotate polarizability tensor depending upon the molecular coordinates?

My question is somewhat related to molecular rotation. I have calculated the polarizability tensor of $\ce{HCHO}$ molecule in PSI4. The output tensor is this, ...
user avatar
5 votes
2 answers
185 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? ...
user avatar
  • 1,256
5 votes
2 answers
204 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 ...
user avatar
  • 1,335
6 votes
1 answer
457 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 ...
user avatar
  • 1,601
6 votes
0 answers
46 views

Compute bulk electrical conducitivity from single-crystal measurements [closed]

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 ...
user avatar
8 votes
1 answer
327 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 ...
user avatar
  • 1,601
10 votes
4 answers
792 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 ...
user avatar
  • 1,335
5 votes
1 answer
244 views

Unrecognized or duplicated keyword error using ORCA

I wanted to run ORCA 5.0.2 with the following input: ...
user avatar
  • 343
7 votes
1 answer
107 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 ...
user avatar
  • 2,461
10 votes
1 answer
134 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 ...
user avatar
  • 303
7 votes
1 answer
64 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?
user avatar
  • 3,599
6 votes
0 answers
51 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 ...
user avatar
  • 869
10 votes
1 answer
81 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 ...
user avatar
11 votes
0 answers
139 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}|\...
user avatar
  • 211
3 votes
1 answer
25 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 ...
user avatar
12 votes
1 answer
387 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 ...
user avatar
10 votes
2 answers
239 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 ...
user avatar
  • 375
7 votes
1 answer
89 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 ...
user avatar
  • 1,335
5 votes
1 answer
147 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}...
user avatar
11 votes
3 answers
717 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 ...
user avatar
  • 821
6 votes
0 answers
62 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 ...
user avatar
  • 1,769
6 votes
0 answers
86 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 ...
user avatar
  • 343
6 votes
2 answers
243 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 ...
user avatar
  • 821
11 votes
2 answers
427 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 ...
user avatar
  • 1,769
6 votes
1 answer
74 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 ...
user avatar
  • 2,293
4 votes
0 answers
89 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 ...
user avatar
  • 111
8 votes
2 answers
69 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 ...
user avatar
9 votes
2 answers
505 views

Visualize electron density using pyscf

I found the following example of code which uses density functional theory to compute the electron density $\rho$: ...
user avatar
8 votes
2 answers
134 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 ...
user avatar
  • 1,942
7 votes
1 answer
134 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 ...
user avatar
5 votes
1 answer
130 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 ...
user avatar
8 votes
1 answer
311 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 ...
user avatar
11 votes
1 answer
524 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 ...
user avatar
9 votes
1 answer
159 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. ...
user avatar