Local MP2 with Density Fitting for Periodic Systems: A Parallel Implementation.

A parallel implementation is presented for the evaluation of local second-order Møller-Plesset perturbation theory (LMP2) energies in periodic, nonconducting crystalline systems with a density-fitting approximation of two-electron repulsion integrals. Peculiarities of the periodic case with respect to parallel LMP2 implementations in molecular codes, such as the use of translational and point symmetry, impose different strategies in order to achieve good parallel performance. The implementation is benchmarked on a few systems, representing a choice of the most interesting solid state quantum-chemistry problems where the MP2 approach can be decisive. Good parallel efficiency of the algorithms is demonstrated for up to 54 processors. Test systems include a metal organic framework (MOF-5) 3D crystalline structure with a triple-ζ-quality basis set: this is the largest calculation performed so far with 106 atoms, 532 correlated electrons, and 2884 atomic orbitals per unit cell.