Efficient sampling of a dual-resolution ensemble by means of dragging

A method to simulate a dual-resolution ensemble for molecular systems is introduced. The dual-resolution system is characterized by an atomistic Hamiltonian and coarse coordinates connected by linear springs to this atomistic system. A ‘dragging’ update scheme based on an idea of Neal (Neal, R. M. Taking Bigger Metropolis Steps by Dragging Fast Variables; Technical Report; University of Toronto: Toronto, Canada, October, 2004; http://arxiv.org/PS_cache/math/pdf/0502/0502099v1.pdf) is proposed. It is theoretically proven that the scheme correctly samples the dual ensemble. As a proof-of-principle we show that in an one-dimensional barrier crossing simulation, the relaxation speeds up by a factor 80. In an asymmetric two-dimensional barrier crossing problem, the speedup is a factor 20. The application to molecular simulations is discussed.