Parallel unrestricted MP2 analytic gradients using the Distributed Data Interface

A scalable distributed-data parallel analytic gradient algorithm for unrestricted second-order Mcircle divideller-Plesset perturbation theory is presented. Features of the implementation using the Distributed Data Interface are discussed in detail. Benchmark timing calculations on a parallel cluster system are presented for a variety of gold cluster molecules. The speedups, parallel efficiencies, and percentage parallelism for these calculations are reported.