Atomistic simulation of size‐dependent heat capacity of liquid in molecular scale confinement at different temperatures

Abstract

An enhancement of heat capacity (C v) of nanoconfined liquid is reported using equilibrium molecular dynamics simulations using Lennard-Jones type solid-liquid molecular model. Liquid molecules are confined in between two solid surfaces with separation distance varying from 0.6 to 17.55 nm and temperature 100 K to 140 K. The obtained heat capacity of the bulk liquid is in excellent agreement with the published literature. However, in case of nanoconfined liquid, for a particular temperature and gap thickness band, a significant enhancement of heat capacity results in. For 100 K temperature and a gap thickness of 4 nm, the obtained molar heat capacity of the nanoconfined liquid is 46.45 J/mol K, i.e. the heat capacity is enhanced by 133% compared to its bulk counterpart (19.95 J/mol K). However, this broad maximum value of heat capacity shifts to a lower value at a higher temperature. At 120 and 140 K, the maximum heat capacity becomes 29.56 and 26.97 J/mol.K and the enhancement becomes 51% and 40%, respectively. The enhancement of heat capacity is attributed to the variation in density distribution, ballistic transport of thermal phonons, reduced molecular motion and a larger contribution of interfacial thermal resistance.