The path-integral monte carlo of rigid linear molecules in three dimensions

The applicability of the path-integral Monte Carlo (PIMC) method to the description of quantized orientational degrees of freedom of rigid linear molecules in three dimensions is discussed. Special attention is payed to the sign problem. It is shown that the sign problem is severe for anti-symmetric rotational states at low temperatures, while it is completely absent in the case of symmetric and nonsymmetric rotational states. The presented PIMC method is applied to a model potential. Using higher order correction terms according to the Takahashi Imada algorithm, even tunneling anomalies in the specific heat could be computed to very high numerical precision.