SYSTEM RELAXATION AND THERMODYNAMIC INTEGRATION

The thermodynamic integration (TI) method for calculating free energy differences has three inherent problems: statistics, numerical integration, and relaxation. In this paper the latter is analyzed for the nonequilibrium TI method introduced by Postma which combines molecular dynamics simulation and TI in a very effective way. A nontrivial extrapolation technique is presented to remove the relaxation error and to calculate the underlying relaxation time. It is shown that the optimal choice of grid points, derived in a previous paper, for minimizing statistical errors not only removes integration errors, but also minimizes relaxation errors. The methods are applied in a calculation of the free energy of cavity formation in water. © 1992, Taylor & Francis Group, LLC. All rights reserved.