THE JACOBIAN FACTOR IN FREE-ENERGY SIMULATIONS

The role of Jacobian factors in free energy simulations is described. They provide a simple interpretation of ''moment of inertia correction '' and ''dynamic stretch free energy'' terms in such simulations. Sinc e the relevant Jacobian factors can often be evaluated analytically by use of the configurational partition function of a polyatomic molecul e, it is possible to subtract them from the simulation results when th ey make unphysical contributions. An important case arises in alchemic al simulations that use a single topology method and introduce dummy p articles to have the same number of atoms in the initial and final sta te. The more general utility of the Jacobian factors for simulations o f complex systems is briefly discussed. (C) 1996 American Institute of Physics.