Fragment Molecular Orbital Molecular Dynamics With Periodic Boundary Conditions on the Blue Gene/P

Kurt Brorsen, Iowa State University

The fragment molecular orbital (FMO) method has been previously combined with molecular dynamics and periodic boundary conditions (FMO-MD-PBC) to facilitate fully ab initio molecular dynamics calculations of bulk properties. Previous implementations of FMO-MD have neglected contributions to the gradient of the response terms that arise from the external electrostatic potentials. The neglect of these response terms has resulted in poor energy conservation for the NVE ensemble. Recently, the Z-vector equations for FMO have been derived and the additional response terms have been added to the gradient. The FMO-MD-PBC implementation in the GAMESS program is modified to run on the IBM Blue Gene/P with fully analytic energy gradients. It is shown that this results in perfect energy conservation for FMO-MD in the NVE ensemble. Timing information and preliminary calculations on water are presented.

Abstract Author(s): Kurt R. Brorsen, Noriyuki Minezawa, Mark S. Gordon