Heat conduction in liquids involving many-body potentials (contribution of inter- And intramolecular energy transfer)

The molecular dynamics expression of heat conduction flux, which was originally derived by Irving and Kirkwood (1950) for pair-wise potentials, is generalized to systems with many-body potentials defined. The formula, newly derived in the present report, consists of kinetic part and potential part, and the latter term is expressed as a summation of thermal energy transfer in each group of interaction sites for which a many-body potential is defined. Next, the mechanism of the thermal energy transfer involving many-body potentials is clarified by extending the concept of intermolecular energy transfer previously proposed by one of the authors, and the accumulation of the thermal energy transfer over all the potentials and interaction sites in the system is proved to make up the potential part of the expression. A molecular dynamics simulation is conducted for liquid n-octane to examine the applicability of the expression newly obtained, and the contributions of the inter- and intramolecular potentials to heat conduction are elucidated.