Questions tagged [hartree-fock]
For any questions about (or related to) the Hartree-Fock method.
18
questions
6
votes
1answer
140 views
Convert reduced density matrix from M.O. to A.O. basis
I am interested in converting the one-particle reduced matrix (rdm1) from the molecular orbital (M.O.) basis to the atomic orbital (A.O.) basis. Is the following method correct (in an identical ...
7
votes
1answer
62 views
Visualize electron density using pyscf
I found the following example of code which uses density functional theory to compute the electron density $\rho$:
...
9
votes
1answer
118 views
'Exchange' in Hartree-Fock and Kohn-Sham DFT
I am a bit confused about the notions of exchange in the Hartree-Fock and Kohn-Sham Density Functional Theory schemes.
In Hartree-Fock, one just writes down the many-electron wavefunction as a hartree-...
8
votes
3answers
225 views
Does Kohn-Sham DFT use Slater determinants?
In the Hartree method, it is known that the wavefunction of the system does not obey the antisymmetry principle of fermions - that is when you swap two particles, they don't up a negative sign. ...
14
votes
1answer
360 views
Why is CPHF/CPKS necessary for calculating second derivatives?
This question is coming from an answer to one of my previous questions. During optimizations, QM programs usually compute the gradient(first derivative) analytically, and take a guess of the hessian (...
12
votes
2answers
184 views
Optimization of Gaussian basis sets within the Hartree-Fock Method
I am revisiting some exercises in Thijssen's Computational Physics book, particularly chapter 4 on the Hartree-Fock method. I am interested in the method of nonlinear optimisation for its own purposes,...
6
votes
1answer
220 views
Why is my quantum chemistry software not printing as many 2e- integrals as I expect?
Background:
In Hartree-Fock theory, the two-electron integral is given by:
$[ij|kl]$ = $\int dx_{1}dx_{2}(\chi_{i}(x_{1})\chi_{j}(x_{1})\frac{1}{r_{12}}\chi_{k}^{*}(x_2)\chi_{l}(x_{2})$
I am ...
9
votes
2answers
252 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):
...
8
votes
1answer
164 views
Semi-canonicalisation vs canonicalisation of the Fock matrix and orbitals
I have seen the terms semi-canonicalized and canonicalized used in relation to the Fock matrix, density matrices, and orbitals; however, I am unsure what these terms actually describe.
For instance:
...
9
votes
1answer
113 views
Muonic Modeling
I have seen an article[1] that describes a HF approach to working with exotic muonic atoms. I am curious about how far DFT has been extended for modeling muonic chemistry. Are there psuedopotentials ...
18
votes
5answers
469 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 ...
12
votes
1answer
157 views
Analog computing in matter modeling today: Any applications?
When we think about computers and computing today, almost invariably we think about digital computers, the ever-present objects today. But reading this question in the Chemistry stackexchange, How are ...
11
votes
1answer
247 views
How to calculate the Fock matrix in the molecular orbital basis PySCF?
I am interested in calculating the Fock matrix in the molecular orbital basis with PySCF, though I am not clear on the methodology behind this task.
In my attempt, I use the following script (for the ...
12
votes
2answers
595 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:
...
15
votes
2answers
458 views
Hartree-Fock density vs Kohn-Sham density
Hartree-Fock density is free of self-interaction but lacks electron correlation effects, while the density from KS-DFT (using an xc functional or potential, both which are explicitly density-dependent ...
11
votes
2answers
241 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
158 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
487 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 ...
