Optimized Constant Pressure Stochastic Dynamics

A recently proposed method for computer simulations in the isothermal–isobaric (NPT) ensemble, based on Langevin-type equations of motion for the particle coordinates and the “piston” degree of freedom, is rederived by straightforward application of the standard Kramers–Moyal formalism. An integration scheme is developed that reduces to a time-reversible symplectic integrator in the limit of vanishing friction. This algorithm is hence expected to be quite stable for small friction, allowing for a large time step. We discuss the optimal choice of parameters, and present some numerical test results.