Questions tagged [self-consistent-field]

For questions related to performing calculation using the self consistent field (SCF) algorithm, for example Hartree-Fock and Kohn-Sham Density Functional Theory.

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10
votes
1answer
224 views

How to make sure that my SCF calculation is correct?

hope you are doing well. I am trying to study the electronic properties of ZnO doped with transition metals (Co, Ni, Fe) using DFT calculation, I am a beginner on DFT calculation using quantum ...
9
votes
1answer
100 views

Should I use a lower threshold for calculations involving SOC?

I'm studying a compound $\ce{VSe_2}$ using the DFT package Quantum ESPRESSO (QE). The following is the input file. ...
15
votes
3answers
155 views

How is “basis set projection” done?

I recently came across something called the basis set projection in Q-chem's manual. What it seems to do is to take the converged SCF in a smaller basis set, and then "projects" that onto a ...
12
votes
2answers
220 views

Getting different total magnetic moment in 'scf' and 'vc-relax' calculations in Quantum ESPRESSO

I am performing a spin polarized DFT calculations in Quantum Espresso on a Co2MnSi ferromagnetic crystal. For this I have performed these steps: 1) Performed ...
13
votes
2answers
769 views

What is nscf calculation in Quantum ESPRESSO?

I have been using 'nscf' for DOS calculation since it is faster and therefore possible to use a higher kpoints. But why is it faster? why not use it in the place of 'scf'?
8
votes
0answers
76 views

How to do a Delta SCF calculation using ABINIT?

I am trying to optimize the crystal structure based on Delta SCF. But I am not so familiar with ABINIT at all. As the ABINIT website do not provide further information. It would be super nice if ...
9
votes
2answers
253 views

How to choose pseudopotential for DFT calculations in Quantum ESPRESSO?

I am a beginner and newly started running DFT calculations to find out the electronic band structure of certain materials in Quantum ESPRESSO. But we have to select the pseudopotential for running the ...
9
votes
2answers
229 views

Normalization constant and Roothaan Equations

Roothaan Hall Equations: The Hartree-Fock equations are a set of modified Schrodinger equations: $f_{i}\psi_{m}=\epsilon_{m}\psi_{m}$ where: The Fock operator ($f_{i}$) is given by (restricted case): ...
14
votes
1answer
180 views

Standard values for level of convergence

In matter modelling we use self consistent approaches for calculating different properties. Many DFT codes find the ground state of the system by determining total energy self consistently. Going ...
18
votes
5answers
375 views

What are the types of SCF?

Many of us know the most common types of SCF (though we can do better than Wikipedia at explaining them): RHF (Restricted Hartree-Fock), RKS (Restricted Kohn-Sham) [link to answer] UHF (Unrestricted ...
16
votes
3answers
167 views

What are the types of MCSCF?

Similar to: What are the types of SCF? What are the types of Quantum Monte Carlo? What are the types of ab initio Molecular Dynamics? What are the types of pseudopotentials? What are the types of DFT?...
12
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2answers
549 views

What do the rows and columns of a Fock matrix represent?

I am using the pyscf code, where the Fock matrix can be obtained by: ...
10
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2answers
88 views

Which SCF energy to use to plot PES after calculations with SMD?

I have a series of molecules calculated (DFT PBE0-D3/def2-TZVP performed in Q-Chem) and I'm ready to plot PES (Potential Energy Surface). I had to increase the grid to get rid of small imaginary ...
11
votes
2answers
234 views

One-center two-electron integrals between 1s STO

As per @user1271772 's suggestion I am asking this question here again. I am trying to understand SCF cycle by trying to code up solved example from Quantum Chemistry by Levine (page 443, 5th edition)...
11
votes
2answers
147 views

What is the mathematical condition that ensure that the self-consistent field (SCF) procedure must converge?

We know that there is convergence issue of DFT method on study real molecular system. It would be conducive if people could pre-determine if the SCF procedure is converge analytically before starting ...
15
votes
2answers
461 views

How does the Hartree-Fock method improve on Hartree after considering the wavefunction that takes the anti-symmetry property into account?

I am not able to understand the math of this. After taking the Slater determinant as a wavefunction in Hartree-Fock, does the procedure to find wavefunctions remain the same as in the Hartree method ...
9
votes
4answers
217 views

What programs can do electron integrals and SCF calculations with more than one CPU?

Similar to this question which asks for each answer to provide one software that can do CASSCF: I am interested in software that can do integrals, SCF (Hartree-Fock), and the integral transformation, ...
14
votes
2answers
134 views

Convergence by energy and/or density?

The SCF is an iterative procedure to produce the ground state energy and wavefunction for Hartree-Fock, MCSCF, and DFT. Due to the iteration, one needs to establish convergence criteria. Depending on ...
20
votes
4answers
402 views

Difficult cases for converging Kohn-Sham SCF calculations

In a recent article by Woods et. al.[1] a couple of methods for converging ground-state Kohn-Sham DFT calculations are reviewed and compared. In their test suite they give plenty of examples for badly ...