Collection of codes used for quantum chemistry calculations based on Hartree-Fock and Coupled Cluster (CC) methodologies. These are all my own codes developed for learning and testing purposes.
Contents of Repository:
CC_matlab - most up-to-date set of non-relativistic, spin-integrated coupled-cluster codes compatible with molecular orbital (MO) integrals obtained from any commercial quantum cheimstry software (any SCF reference including RHF, UHF, ROHF, and even Kohn-Sham orbitals may be used). Also contains SCF solvers so that MO integrals can be generated in a self-contained manner, although there is currently no symmetry adaptation. Currently supported calculations include:
- RHF + Analytical Gradients
- CCSD + Left-CCSD
- EOMCCSD + Left-EOMCCSD
- CR-CC(2,3) + CR-EOMCC(2,3)
- CCSDT
- CCSDT(III) active-space variant
Routines can be run using one- and two-body molecular orbital integrals inputs (along with system parameters like number of occupied and unoccupied alpha/beta electrons) which can be found in CC_matlab_tests. Run routines as shown in main.m
Numerov - Matlab implementation of the Numerov-Cooley algorithm for numerically integrating the 1D Schrodinger equation. The main.m script applies this method to solve for the 1D vibrational eigenstates of the H2 stretching motion using a simple restricted Hartree-Fock (RHF) potential energy surface.
CT_Hamiltonian - collection of codes used for crude modeling of charge-transfer processes in dimers
Davidson_matlab_test - Matlab implementation of davidson diagonalization routines. Used in EOMCC matlab codes
gaussian_integrals - Fortran implementation of McMurchie-Davidson atomic orbital integral evaluation scheme. I largely translated the Python implementation originally written by Joshua Goings https://github.com/jjgoings/McMurchie-Davidson
hf_python_v* - My initial Python implementation of Hartree-Fock (with integral routines directly taken from Joshua Goings again) which lead into spinorbital CCSD and EOMCCSD. Big and unwieldy code which is streamlined and properly implemented in CC_matlab.
Davidson_test - Python implementation of Davidson routine (use Matlab versions as they are more stable)
Permutation Sign - Useful function for evaluating the sign of a permutation
Tensor Contraction - An exercise in unravelling the amazing Numpy einsum function and writing my own einsum from scratch
Wicks_Theorem_v2 - An attempt at creating a Wick's Theorem evaluation engine for automated equation derivation in coupled-cluster methods. Not exactly complete (or fast) but can evaluate fully-contracted second-quantized expressions and classify the results in Hugenholtz diagrams