Unphysical Heat Transfer by Molecular Dynamics

Abstract

Molecular Dynamics (MD) simulations based on classical statistical mechanics allow the atom to have thermal heat capacity. Quantum mechanics (QM) differs in that the heat capacity of atoms in submicron nanostructures vanishes. Nevertheless, MD simulations of heat transfer in discrete nanostructures are routlinely performed and abound in the literature. Not only are discrete MD sumultions invalid by QM, but give unphysical results, e.g., thermal conducitvity in nanofluids is found to exceed standard mixing rules while in solid metal films depends on thickness. QM explains the unphysical results by negating the heat capacity of atoms in discrete nanostructures, thereby precluding the usual conservation of absorbed electromagnetic (EM) energy by an increase in temperature. Instead, the absorbed EM energy is conserved by QED inducing the creation of non-thermal EM radiation inside the nanostructure that by the photoelectric effect creates charge in the nanostructure, or is emitted to the surroundings. QED stands for quantum electrodynamics. Unphysical results occur because the QED induced radiation is not included in the nanoscale heat balance, but if included the physical results for discrete nanostructures are found. Examples of unphysical MD simulatons are presented.