MEGALOchem is a quantum chemistry program that specializes in and provides tools for low scaling electronic structure methods for ground and excited states in the atomic orbital basis. It is MPI parallel and supports sparse matrix multiplication and tensor contractions via the DBCSR library.

Features:

1. Local density fitting algorithms (Coulomb-attenuated, PARI, quasi-robust density-fitting)
2. Linear scaling Hartree-Fock, SOS-MP2 and SOS-ADC(2)
3. Foster-Boys orbital localization
4. MPI-parallel incomplete Cholesky decomposition with complete pivoting

Go here for documentation.

You can also look at the accompanying PhD thesis for more details on theory here