Monte-Carlo simulations of rotating clusters

A new scheme for estimating densities of states at non zero angular momentum is proposed, using the Monte-Carlo (MC) and multiple histogram methods. It is based on a rigorous expression of tilt classical density of states for a rotating system. Two features appear: the centrifugal energy L.I-1L/2 (L angular momentum and I the instantaneous inertia tensor in the center of mass reference frame) is added to the potential energy and the configurational densities of states is weighted 1/root det I. Comparing the MC results for the 13-atom Lennard-Jones cluster and a calculation based on molecular dynamics (MD) shows that this weight is important if the rotation induces a structural change at a finite temperature. The MC algorithm proves to be much more efficient than MD, even at finite L.