ABSTRACT
The most time-consuming part of multiscale simulations of materials and bio-molecular systems is the quantum mechanical (QM) calculation of forces in a chemically active region. We describe here a method for reducing this computational effort through the use of a sequence of QM and classical approximations. The strategy is to use the more costly but more accurate approximations at relatively infrequent simulation steps to reset the forces from the faster approximations of lower accuracy. We illustrate with a severe test, comprised of only two grades, namely a published classical pair potential and a QM method independently calibrated to reproduce relevant coupled-cluster forces.
