Large scale FMO-MP2 calculations on a massively parallel-vector computer

The fragment molecular orbital (FMO) calculations have been successfully applied to a variety of realistic biochemical problems, by using our original Abinit-mp program. In these applications, the inclusion of electron correlation through the second-order Møller-Plesset perturbation (MP2) was demonstrated to be essential to obtain qualitatively correct descriptions. Recently, the FMO calculations in Abinit-mp were tuned for a massively parallel-vector processing. A series of FMO-MP2/6-31G calculations were performed on the Earth Simulator by which up to 4096 vector processors are available. The largest FMO-MP2 computation was carried out for an influenza hemagglutinin antigen–antibody system consisting of 921 residues, which was completed within one hour with 4096 processors.