Questions tagged [pyscf]

For questions about the PySCF electronic structure module for Python

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7
votes
0answers
48 views

How can I calculate the exchange energy for a molecule in PySCF?

I am trying to generate exchange energy separately in pyscf but didn't see a way to do that. For correlation energy, it's fairly simple but do you have any idea how to calculate exchange energy?
7
votes
1answer
218 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
94 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
votes
1answer
100 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
votes
1answer
300 views

How are 1-electron and 2-electron integrals done in PySCF?

I am right now using the PySCF for some quantum chemistry problems. I need to get the parameters, which are labeled $h_{ij}$ and $V_{ijkl}$. How can I get this done with PySCF?
4
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1answer
77 views

PySCF: 2-index and 3-index matrix

The 4-index 2-electron integral can be obtained for the He atom with the following code: ...
7
votes
1answer
255 views

PySCF: Implementing SHCI frozen argument

I am trying to run a SHCI calculation in PYSCF with DICE; however, I want to freeze the first two core orbitals and the highest 3 virtual orbitals in a calculation. In other parts of PySCF this can ...
5
votes
1answer
185 views

PySCF: atomic basis Fock matrix changes after mo_coeff update

I've noted a curious thing with PySCF when updating the molecular orbital coefficients of the mean-field object. If one prints out the Fock matrix in the atomic basis (...
6
votes
1answer
275 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
1answer
129 views

PySCF: eigenvalues, non-integer occupation, CISD calculations, and frozen lists

I have been performing CISD calculations with PySCF and I have a query surrounding the occupation of the orbitals. Here, the occupancies are calculated from the eigenvalues of the 1-electron ...
10
votes
4answers
796 views

Codes for post-processing Gaussian cube files?

I have generated MOs of a molecular system and I need to recreate its electronic density via $\rho(r)=\sum_{A_i}|\psi_i(\mathbf{r})|^2$ where $A$ is a set of occupied MOs. I am trying to do this via ...
9
votes
1answer
384 views

What unit of energy does PySCF use?

The documentation for PySCF can be found here: https://sunqm.github.io/pyscf/ However, it does not explicitly state in the documentation what unit of energy is used. Is there a way to find this out?
11
votes
1answer
321 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
623 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: ...