The computational methods we develop are collected in ERGO software package. We have published a paper in J. Chem. Phys. which describes some of the linear-scaling properties of the package. As of April 2008, ergo can do following:
Ergo can compute electron densities using Hartree-Fock and Kohn-Sham models. We believe ergo is the first ab initio quantum chemistry program that uses memory and CPU resources proportional to the system size. This allowed us to simulate systems of size approaching 10000 atoms and 67000+ basis functions on a single computer. This was possible due to sparse matrix representation introduced by us throughout entire program. Sparse matrices are generally challenging to implement right as the sparsity enforcement introduces errors that must be diligently controlled.
Property calculations are the ultimate goal of ERGO development: we want to be able to predict molecular properties and aid the development of new molecules. ERGO can currently compute some ground state electron density related properties (like dipole moment) in entirely linear time and memory regime. It can also evaluate linear response properties in essentially linear time up for a range of systems, although the theoretical foundation for calculations linear in both time and memory has been laid. The current implementation is flexible enough to allow for easy extension to higher orders.
The quality of the Kohn-Sham calculations is determined by the used exchange-correlation functional. ERGO currently implements 35 different xc functionals, and another 95 functionals are in the testing and evaluation phase.