Generating integrals

HANDE can treat systems other than model Hamiltonians by reading in the necessary integrals in the FCIDUMP format [Knowles89]. Many quantum chemistry packages can generate them following Hartree-Fock calculations, including:

HORTON

https://theochem.github.io/horton/

MOLPRO

https://www.molpro.net/

PSI4

http://psicode.org. Requires the fcidump plugin (https://github.com/hande-qmc/fcidump).

Q-Chem

http://www.q-chem.com. FCIDUMP code contributed by Alex Thom.

We most frequently use PSI4 and Q-Chem and so these tend to be better tested. Note that the computational cost of the calculations in HANDE vastly outweighs the cost of the underlying SCF calculations and so the efficiency of the code used to generate the integrals is usually not a key factor. Please consult the documentation of the code of interest regarding how to run SCF calculations and generate the integrals in the FCIDUMP format.

The format of the FCIDUMP file expected by HANDE is documented in the comments to src/read_in.F90; these might be useful for users wishing to generate integrals from upon a specific Hamiltonian to feed into HANDE.

Warning

The single-particle basis is assumed to be orthonormal.