Efficiency of Monte Carlo methods for densities and sums of rovibrational states

► Rovibrational densities and sums of states are computed for fully coupled systems using generalized ensemble Monte Carlo methods, including Wang-Landau and virtual-move parallel tempering. ► Illustrations are presented to several molecules for which anharmonic force fields have been determined using high-level quantum chemistry calculations. ► By carefully assessing the performances of the methods against exact results, the Wang-Landau and kinetic Monte Carlo methods are recommended as the most efficient. ► A simple application to an isomerization rate of protonated pyrene, in which the various roles of anharmonicities in the reactant and transition state are evidenced.