Abstract:
A heat jet approach for atomic simulation at finite temperature in both local space and time was proposed based on the 2-way boundary condition and phonon heat bath, without any dissipation factor and empirical parameter introduced. A subsystem was extracted from a space lattice for analysis of the exact molecular dynamics lest the entire lattice was to be solved numerically. For an extracted linear harmonic chain, the 2-way boundary condition allowed effective incoming waves fully enter the subsystem, and meanwhile, non-thermal motion and thermal fluctuation propagate freely out of the subsystem, to realize dynamic equilibrium of the system energy. During numerical calculation, the 2-way boundary condition worked like a wave diode which let in the positive-going waves while keeping out the negative-going ones. The normal mode of phonon heat bath well described the atomic heat vibration, then it was decoupled into positive-going and negative-going input waves of which the former was used to build the heat source term. For the molecular dynamics simulation of linear harmonic chains, the numerical tests demonstrate effectiveness of the proposed heat jet approach, which makes the chain rapidly reach the expectant temperature, keeps it in a steady state thereafter, and reasonably depicted the additional non-thermal atomic motion at finite temperature.
