THE CALCULATION OF FREE-ENERGY DIFFERENCES BY CONSTRAINED MOLECULAR-DYNAMICS SIMULATIONS

In this paper we set out to derive a relation between the constraint f orce and the derivative of the free energy for a system in which only the reaction coordinate is constrained. Our result differs from the ex pression by Mulders et al. [J. Chem. Phys. 104, 4869 (1996)] because w e take into account the effect of the constraint on the sampled phase- space distribution. The method is illustrated with two prototypical nu merical examples. (C) 1998 American Institute of Physics.