Calculation of heat capacities of light and heavy water by path-integral molecular dynamics

Shiga, Motoyuki   ; Shinoda, Wataru*

In general, it has been a difficult issue to evaluate heat capacities of liquids and solids based on interatomic forces. This is because heat capacity involves a strong quantum effect especially at low temperatures. For example, it is known that conventional classical molecular dynamics method overestimates the heat capacity of water. In this report, we show that heat capacity can be calculated by path integral molecular dynamics method considering the quantum effect. The calculated heat capacities for the three states of water and its isotope effect have been found in good agreement with experiment at wide temperature range.