In the 1950s, Metropolis and Teller pioneered molecular dynamics (MD) as a method to derive the thermodynamic and transport properties of bulk molecular liquids. Submicron ensembles comprising a few hundred atoms with periodic boundary conditions were used to derive the bulk liquid properties. Even though the ensembles were submicron, the periodic boundary conditions allowed the heat capacity of the atom at wavelengths longer than the dimensions of the ensemble to be included in the MD simulations.

Today, MD simulations have been extended almost entirely to discrete submicron structures. See WTC IV The implicit assumption in the later MD simulations was there is no difference between the thermal heat capacity of the atoms in the discrete submicron structures and those ensembles in MD simulations with periodic boundary conditions.

However, quantum mechanics (QM) as embodied in the Einstein-Hopf relation shows the thermal heat capacity of the atom as given by the Planck energy of the harmonic oscillator depends on dispersion with wavelength. At ambient temperature, most of the thermal heat capacity of the atom is available at wavelengths > 100 microns where the thermal kT energy is about 25.8 meV. But the thermal emission from atoms in submicron structures is confined to wavelengths < 1 micron, and therefore excludes almost all of the heat capacity of the atom. Alternatively, atoms in discrete submicron structures in MD simulations lack the heat capacity necessary to conserve absorbed EM energy by an increase in temperature.

MD simulations of discrete submicron ensembles may proceed as usual provided the QM restriction on the heat capacity of the atoms is properly simulated. One such method is the theory of QED induced radiations. See QED radiations Lacking the heat capacity to conserve absorbed EM energy by an increase in temperature, the absorbed EM energy is frequency up or down-converted by QED to the EM confinement frequency of the submicron structure. Subsequently, the absorbed EM energy is conserved by the emission of non-thermal EM radiation.