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.