This is an exact solver for double occupied configuration interaction (DOCI). It builds the hamiltonian using compressed row storage (sparse) and uses lanczos (or fully diagonalization) to find the lowest eigenvalue and eigenvector. Using that eigenvector, it than builds the second order reduced density matrix (rdm) and stores it in a HDF5 file. It only builds the elements of the rdm that can be non-zero for DOCI.

Build

To build this, you need a C++11 compiler (gcc 4.8 or newer, clang 3.3 or newer), the HDF5 libraries, the blas and lapack libraries and the arpack library. The Makefile is quite simple, adjust the compilers and header/libraries as needed for your system.

Input

The program needs molecular integrals from PSI4. You can extract them using a plugin: https://github.com/wpoely86/doci_sdp-atom/blob/master/extern/mointegrals.cc

Documentation

Everything is documented with doxygen. Run make doc to build the HTML docs. Or read the docs online. If something is unclear, do not hesitate to contact me.

License

The code is available under the GPLv3 license.