Rigid body molecular dynamics with nonholonomic constraints: Molecular thermostat algorithms

Generalized Euler equations and center of mass equations are derived to describe the motion of a rigid body under general nonholonomic constraints. These equations provide a basis for developing algorithms for rigid body molecular dynamics (MD) simulations with nonholonomic constraints. In particular, two distinct molecular thermostat algorithms for constant temperature rigid body MD simulations are described. Both algorithms ensure satisfaction of the temperature constraint at every MD time step, without introducing additional numerical errors into the center of mass velocities or angular velocities. Results from constant temperature MD simulations of a system of 500 methylene chloride (CH2Cl2) rigid molecules using both thermostats are presented, exhibiting their efficiency and accuracy. finally, a generalized Gauss's principle of least constraint is derived, to establish a formal connection between the molecular approach described hers for incorporating nonholonomic constraints in MD simulations and previous atomistic approaches.