Higher-order correlated calculations based on fragment molecular orbital scheme

We have developed a new module for higher-order correlated methods up to coupled-cluster singles and doubles with perturbative triples (CCSD(T)). The matrix-matrix operations through the DGEMM routine were pursued for a number of contractions. This code was then incorporated into the ABINIT-MPX program for the fragment molecular orbital (FMO) calculations. Intra-fragment processings were parallelized with OpenMP in a node-wise fashion, whereas the message passing interface (MPI) was used for the fragment-wise parallelization over nodes. Our new implementation made the FMO-based higher-order calculations applicable to realistic proteins. We have performed several benchmark tests on the Earth Simulator (ES2), a massively parallel computer. For example, the FMO-CCSD(T)/6-31G job for the HIV-1 protease (198 amino acid residues)-lopinavir complex was completed in 9.8 h with 512 processors (or 64 nodes). Another example was the influenza neuraminidase (386 residues) with oseltamivir calculated at the full fourth-order Moller-Plesset perturbation level (MP4), of which job timing was 10.3 h with 1024 processors. The applicability of the methods to commodity cluster computers was tested as well.