CONSTANT-PRESSURE MOLECULAR-DYNAMICS SIMULATION - THE LANGEVIN PISTONMETHOD

A new method for performing molecular dynamics simulations under const ant pressure is presented. In the method, which is based on the extend ed system formalism introduced by Andersen, the deterministic equation s of motion for the piston degree of freedom are replaced by a Langevi n equation; a suitable choice of collision frequency then eliminates t he unphysical ''ringing'' of the volume associated with the piston mas s. In this way it is similar to the ''weak coupling algorithm'' develo ped by Berendsen and co-workers to perform molecular dynamics simulati on without piston mass effects. It is shown, however, that the weak co upling algorithm induces artifacts into the simulation which can be qu ite severe for inhomogeneous systems such as aqueous biopolymers or li quid/liquid interfaces.