The rotational centroid and its application in quantum molecular dynamics simulations

The centroid molecular dynamics (CMD) method is extended to the rotational motion of rigid bodies. An algorithm is developed that homogeneously samples the orientational neighbourhood associated with the quantum degrees of freedom of a specified orientational centroid and by design ensures the constancy of the centroid. As part of this development a general definition for an orientational centroid (or average rotation), as well as a procedure to determine it, are presented. The application of this CMD methodology in quantum simulations of rigid body systems is discussed and demonstrated for a simple system.