Generalization of Nosé’s isothermal molecular dynamics

A generalization is given of the method introduced by Nos\'e for simulating isothermal behavior by molecular dynamics. An infinity of physically inequivalent choices for dynamics can be made to evaluate average properties of an equilibrated canonical ensemble. The availability of different choices may, we suggest, open the principal possibility of searching for a dynamics which will adequately mimic not only the equilibrium but also the time-dependent properties of a particular physical system.