A new direct MP2 gradient algorithm with implementation on a massively parallel computer

A new direct second-order Mّller-Plesset gradient algorithm is presented. By avoiding generation of molecular orbital integrals with three virtual indices, the memory requirement for a calculation with n basis functions and o occupied orbitals is reduced to on2, and overall computational savings are obtained. The algorithm has been implemented with distributed data on a massively parallel computer, the Intel Paragon. The parallelization scheme provides high parallel efficiency, and the performance of the algorithm is illustrated for calculations running on up to 64 processors.