Closed RichRick1 closed 2 years ago
Gerald Knizia has a code for Hubbard models. http://www.iboview.org/bin/bethe_ansatz.20140603.tar.bz2
This program can calculate a number of (exact) ground state properties of the infinite 1D Hubbard model, at arbitrary fillings (n) and couplings strengths (U), using the Bethe Ansatz solution. Supported are energies/site, chemical potentials, metal-insulator transitions (1-particle gaps), and on-site spin correlation functions/particle number correlation functions.
Background: The 1D Hubbard model is one of the few exactly solvable model systems for strong correlation; this program computes reference data against which new electronic structure programs can be compared.
This is from Gerald's website. https://sites.psu.edu/knizia/software/
The Pariser-Parr-Pople parameters are given explicitly for benzene here. https://www.sciencedirect.com/science/article/pii/0009261488803749?via%3Dihub See below equation 8.
A few other possibly useful references. This one has explicit formulations of the occupations numbers https://aip.scitation.org/doi/10.1063/1.1425408
and this is also maybe useful https://journals.aps.org/prb/pdf/10.1103/PhysRevB.30.4267 https://hrcak.srce.hr/file/166534 https://arxiv.org/pdf/physics/0207086.pdf
So far there are implemented (not int the best way):
The main method is
get_hamilton
which returns zero, one and two body integrals as Numpy arrays.Problems appears when testing an existing code. So far, there are couple of tests.
All code is available here: https://github.com/theochem/ModelHamiltonian/blob/upd/upd/Huckel_Hamiltonian.py