Skip to main content

Questions tagged [electronic-structure]

For questions concerning electronic structure concepts and calculations.

Filter by
Sorted by
Tagged with
1 vote
0 answers
15 views

Temperature dependent Structural and electronic Properties in Quantum espresso

I want to calculate temperature properties of hexagonal materials. Specifically, I want to know how lattice parameters, bond lengths and atomic positions changes. Further I want to compute thermal ...
Rafi Ullah's user avatar
3 votes
0 answers
39 views

How to compute molar Gibbs free energy (chemical potential) for single molecule using gaussian09?

I want to calculate the Gibbs free energy of single gas molecule (AsH3) using Gaussian 09, but I am confused between "Thermal correction to Gibbs Free Energy" and "Sum of electronic and ...
Abhishek's user avatar
12 votes
4 answers
987 views

Are there non-antisymmetric solutions to the electronic Hamiltonian?

In electronic structure theory, one seeks solutions of the molecular electronic Hamiltonian $$ H_e(\vec{R}) = T_n(\vec{r}) + V_{ne}(\vec{r};\vec{R}) + V_{ee}(\vec{r}) + const, $$ where $\vec{r}$ are ...
Solarflare0's user avatar
4 votes
0 answers
85 views

t2g-eg resolved PDOS analysis [duplicate]

I was attempting to analyze the t2g-eg resolved PDOS for transition metal-containing systems. Here, I have taken an example where three types of transition metals are present in octahedral geometry: $...
Kratos1611's user avatar
8 votes
3 answers
224 views

Different results from MP2 calculations on same geometry in ORCA

I am trying to do a segmented potential energy scan around a dihedral for a molecule. I have optimized the geometry to a minima, and the scan runs from [-180, 180] in steps of two points at a time. ...
Hemanth Haridas's user avatar
3 votes
1 answer
90 views

what determines the 'Estimated total dynamical RAM ' in a Quantum Espresso calculation

As per my understandings the computer resources required for a DFT calculation increases by an order of three with the number of atoms. But as you can see in the output files given below the ...
Joyal sunny's user avatar
0 votes
1 answer
45 views

In which irreducible representations shall I put the electrons in an F atom in PySCF?

I’m looking to complete ROHF energy calculations in PySCF for the F atom. I need to update the irrep_nelec dictionary for F. I know that the one for the O atom is: ...
TheorVHP's user avatar
1 vote
0 answers
26 views

Applying Pressure in z-direction in quantum espresso

I am working with Bilayer 2H-MoS2, interlayer spacing ~3A. I want to apply pressure in z-direction which can lead to reduction in interlayer spacing, and then calculating its electronic properties. so,...
Hamza Hamza's user avatar
3 votes
1 answer
61 views

How is the form of the active space electronic Hamiltonian derived?

The electronic Hamiltonian in the canonical orbital basis has the following form: $$\tag{1} H_e = h_0 + \sum_{ij=1}^{N} h_{ij} \sum_{\sigma \in \{\uparrow,\downarrow\}} a_{i\sigma}^\dagger a_{j\sigma} ...
Solarflare0's user avatar
15 votes
2 answers
2k views

Why is my hydrogen energy not equal to -0.5 hartrees?

I'm trying to calculate the HOMO of various molecules in water solution. I first tried to see how PySCF calculates the HOMO of hydrogen. I ran the following code: ...
nkam's user avatar
  • 153
7 votes
1 answer
376 views

Why use PySCF/OpenMolcas instead of VASP/QuantumESPRESSO

While I am aware that VASP and QE are widely used for solid-state materials and PySCF/OpenMolcas are primarily designed for molecular systems. I want to know why should I use PySCF/OpenMolcas for ...
Jaafar Mehrez's user avatar
7 votes
1 answer
269 views

Materials with low band gap and low conductivity simultaneously. Is it possible?

I'm working on a data-driven project involving material properties and I'm wondering about the following: I know that the notion of band gap and electrical conductivity are inversely related, and the ...
James Arten's user avatar
2 votes
1 answer
357 views

'The combination of multiplicity electrons is impossible' in Gaussian

I am trying to calculate the energies of the S1 and T1 states of a molecule with UDFT using Gaussian. For the T1 state, I can successfully use the following input file: ...
Laura's user avatar
  • 1,267
5 votes
1 answer
40 views

How to Model Cations or Anions for Activation Energy Barrier Calculation in VASP for Electron Exchange Reactions?

I am interested in performing activation energy barrier calculations using VASP (Vienna Ab initio Simulation Package) specifically for reactions involving electron exchange. However, I am uncertain ...
Nidhi Tiwari's user avatar
6 votes
0 answers
68 views

What are the parameters in PySCF's Selected Configuration Interaction code

Dear StackExchange Members, I'm using the native PySCF implementation of selected configuration interaction (SCI). However, I can't seem to find any documentation detailing the algorithm or various ...
AWPrentice's user avatar
1 vote
1 answer
92 views

How to use the CI method to compute the order of the molecular orbitals of the nitrogen molecule

It is well known that the Hartree–Fock (HF) approximation predicts a wrong order for the last two molecular orbitals of N$_{2}$. The calculations indicate that the 1$\pi_{u}$ orbital has higher energy ...
AlfredV's user avatar
  • 183
6 votes
2 answers
179 views

How do I get the energy, if I have the wavefunction?

I recently wrote a simple HF SCF program for my understanding and realized that I do not fully understand such QM calculations. Suppose I have the ground state gaussian wave function of a system, $$ \...
ipcamit's user avatar
  • 615
3 votes
0 answers
77 views

How did they calculate the indirect radiative recombination rate in this paper?

In this paper they calculated radiative recombination rates for Germanium using an effective mass model and I am trying to calculate the indirect spontaneous radiative recombination rate related to ...
Peter Pien's user avatar
6 votes
2 answers
399 views

How may I solve the radial Schrödinger equation?

I want to solve the radial Schrodinger equation for a Carbon atom with all six electrons. The equation I want to solve is for $r>0$: $$[\frac{-\hbar^2}{2m}\frac{\partial^2}{\partial r^2}+ \frac{\...
L Maxime's user avatar
0 votes
0 answers
30 views

Spaces in Electronic band structure

I keep getting this whenever I try plotting the electronic band structure for CoRhMnGa on quantum Espresso, what could possibly cause the vertical spaces
Jeremiah Okotie's user avatar
2 votes
0 answers
61 views

Temperature effect on electronic properties

I'm particularly interested in studying how temperature affects electronic properties. However, I've been working with Quantum Espresso and its DFT + U functionality, and I'm struggling to understand ...
Prasad's user avatar
  • 101
7 votes
2 answers
171 views

Why is electron correlation called the "chemical glue"?

A significant part of quantum chemistry involves developing methods that go beyond the Hartree-Fock theory which treats electron-electron interactions through a mean-field approach. From what I ...
Fracton's user avatar
  • 271
7 votes
1 answer
578 views

pyscf: Why should the choice of pseudopotential determine the total energy, and not the physics?

I have limited experience with DFT, but as an exercise I have written a DFT program of an atom (from scratch using nothing more than python built in functions and numpy) by following Richard Martin's ...
Mikke Mus's user avatar
  • 263
3 votes
0 answers
45 views

Reproduce Dissociation Energy of BH molecule with PySCF

I want to reproduce the bond dissociation energy of the BH molecule as stated in the book 'Molecular Electronic Structure Theory' by Helgaker et al, (chapter 8.3.1), using FCI with 1 frozen core ...
jakg's user avatar
  • 31
9 votes
2 answers
412 views

Quantifying relativistic effects in DFT calculations

I am wondering what is the best approach to quantify the contribution of relativistic corrections to a result of an electronic structure calculation. As far as I understand, from a user perspective ...
Szgoger's user avatar
  • 624
2 votes
0 answers
17 views

Can I define molecular units on NBO3.1 or NBO6.0?

I'm studying donor-acceptor charge transfer (CT) process between tetrakis(m2-acetato)-di-Wolframium (acceptor) with an acetonitrile (donor) at the B3LYP-D3BJ/def2-TZVPD level of theory. The W···N ...
Juandiego Velasquez Benites's user avatar
3 votes
0 answers
60 views

What is a relaxed reduced density matrix?

I am trying to understand how to calculate electronic properties using reduced density matrices from electronic structure calculation. So far, I understand (I think) that for the expectation value of ...
Szgoger's user avatar
  • 624
5 votes
1 answer
82 views

How to obtain imaginary frequency polarizability?

I am trying to find a way to calculate $C_6$ dispersion coefficients for some atoms and molecules. In papers and textbooks, this quantity is introduced using the Casimir-Polder integral from the ...
Szgoger's user avatar
  • 624
4 votes
1 answer
158 views

Computing proton-proton potentials for infinite periodic materials

For electronic structure calculation, when optimizing the wavefunction for an infinite periodic material, the proton-proton energy is needed to monitor the convergence of the SCF loop. How is the ...
mle's user avatar
  • 1,031
3 votes
0 answers
25 views

How to get energy gap change at specific high symmetry points during ab initio molecular simulations?

I want to check the energy gap change during finite temperature ab initio molecular simulations. The results may look like this picture: How can set aimd simulation to get this result in VASP?
Tieyuan Bian's user avatar
3 votes
1 answer
76 views

Plane wave expansion of the wavefunction for periodic material modelling

The aim is to do an electronic calculation with static nucleus with Plane wave (PW) basis functions for an infinite periodic material. The number of functions is given by the pairs of reciprocal ...
mle's user avatar
  • 1,031
4 votes
2 answers
301 views

Can the the relaxed energy of a material system (eV/atom) computed by DFT using VASP be positive?

If it is positive, why is it so? Is it due to specific convergence criteria or choice of pseudopotentials? I cannot check the convergence of the DFT calculations as they have been downloaded from a ...
Pranoy Ray's user avatar
  • 1,637
2 votes
1 answer
52 views

Plane-wave basis expansion for periodic material modelling: cutoff energy inequality and number of atoms in the simulation

The calculation of electronic structure of infinite periodic material using Plane-waves is the object of study here. The cutoff energy $E_{cutoff}$ provides information about the accuracy of the ...
mle's user avatar
  • 1,031
4 votes
1 answer
130 views

How to read UPF pseudopotential for ultrasoft pseudopotential simple in a fortran program

I'm currently working on calculating semiempirical local and nonlocal matrix elements for Ga. To proceed with my calculations, I need to extract specific parameters from the UPF (Unified ...
Raj Kumar Paudel's user avatar
5 votes
1 answer
146 views

What do we get by integrating over the charge density data of a material system calculated with DFT?

I am confused as to whether integrating over the charge density gets us the number of valence electrons in the material system or the total number of valence electrons in the material system. Let's ...
Pranoy Ray's user avatar
  • 1,637
4 votes
1 answer
107 views

Unrestricted Hartree-Fock : Density matrices initialization

I have some results about the energy of H2 as a function of the bond length using Restricted HF (RHF) and Unrestricted HF (UHF) methods. With a zero-initialization of the density matrix I have the ...
mle's user avatar
  • 1,031
5 votes
1 answer
269 views

Contents of a CHGCAR file and how to read it appropriately in Python? [duplicate]

Rephrasing the above, what is the content of the data in the CHGCAR file? Is the data part shown below representative of the electron-charge density or is it the actual charge in the system and I have ...
Pranoy Ray's user avatar
  • 1,637
2 votes
1 answer
141 views

ORCA Error: NCalcs not set

I've been getting the following error whenever I use CCSD(T) and the ORCA Forums don't have an answer to this one: ...
znc204's user avatar
  • 63
5 votes
3 answers
267 views

How do I obtain CB and VB values from Quantum ESPRESSO?

Can someone explain to me please how am I supposed to get this: From this: I'm a little bit confused because in my calculations using Quantum ESPRESSO I found that: ...
Camilla's user avatar
  • 2,209
5 votes
1 answer
534 views

What are alpha and beta electrons?

Question The mwfn filetype includes fields for alpha and beta electrons/orbitals/density matrices. What is the definition of alpha and beta electrons; what distinguishes them? For future research, ...
Adam's user avatar
  • 153
6 votes
1 answer
367 views

Which is better for binding energies: DFT-D3 or RI-MP2?

I am trying to calculate the binding energy of a small molecule with an underlying surface. I have used B3LYP-D3BJ (as implemented in ORCA) at def2-TZVP basis set to optimize the geometry of the VdW ...
Hemanth Haridas's user avatar
6 votes
0 answers
54 views

Benchmarking DFT vs Experimental Gaps - Confusion over Fundamental and Optical Gaps

Recently, I've come across discussions about the differences between fundamental (or electronic) bandgaps and optical bandgaps, with the two quantities differing mainly by the electron-hole binding ...
CW Tan's user avatar
  • 1,326
5 votes
1 answer
343 views

Python library to obtain atomic orbitals of atoms in the lowest energy state

I want to code an UHF code. Hence for each atom I need the lowest energy electronic configuration. Is there a python package/library that already does it?
mle's user avatar
  • 1,031
2 votes
0 answers
44 views

PySCF two-electron integrals between two fragments

I am trying to compute integrals of the form $(pq|rs)$ where the orbitals $p$ and $q$ are orthogonalized atomic orbitals for a fragment $A$ and $r,s$ are orthogonalized on fragment $B$. I was thinking ...
Szgoger's user avatar
  • 624
6 votes
1 answer
96 views

Variation of Conduction band minimum and valence band maximum with applied strain in semconductors

I have been using the Deformation Potential theory to evaluate the electron scattering rates in nanomaterials. In each case, I was under the impression that the Conduction Band Minimum (CBM) and the ...
PBH's user avatar
  • 2,653
2 votes
0 answers
85 views

Determination of fluorescence lifetime by using oscillator strength?

$$k_r=2.88\times10^{-9}n^2\langle\tilde{v}\rangle_\text{av}^2 \int\varepsilon_{\tilde{v}}d\tilde{v}$$ $$f=4.32\times10^{-9}\int\varepsilon_{\tilde{v}}d\tilde{v}$$ I plan to use the above equations to ...
Yasir Ulutas's user avatar
3 votes
0 answers
112 views

Inconsistent band structure of bilayer graphene [closed]

Context I am performing band structure calculations for bilayer graphene using QE codes. I used X-crysden for the k-point mesh ...
Akash Saxena's user avatar
2 votes
0 answers
210 views

Graphene Band Structure with SIESTA [closed]

I am struggling with getting a correct band structure for even pristine graphene using SIESTA. The issue is almost certainly the K point path. My graphene sheet (128C atoms) isn't the traditional ...
Elie H's user avatar
  • 1,411
3 votes
0 answers
145 views

Electronic Structure Calculation with External Field

There are various programs for calculating energy states for molecules (ORCA, Gaussian, ...). Is there also software that allows the same simulations with an additional external potential (e.g. ...
Johny Dow's user avatar
5 votes
1 answer
179 views

DFT calculation for conjugated polymers

I am new to DFT calculation. I want to know the structure of conjugated polymers (plane angle, etc.) and their electronic and optical properties (such as HOMO-LUMO, IR, etc.). I am using 6-311+G(d) ...
Duy-Minh Hoang's user avatar