关键词: 氦, 分子动力学, 势能函数, 分子间相互作用

Abstract: In order to find appropriate form of potential function and determine the dimensionless equation for intermolecular force of helium-4 atoms in molecular dynamics (MD)study, mathematical expressions and application conditions are analyzed.The standard LJ potential function (LJ-12-6)is widely used in the MD simulation for the gas with simple structure because of its simple form and satisfactory precision.For helium, the repulsive part of the potential expressed in minus twelve power of r is inappropriate and exponential function is used instead.EXP-6 potential is one of the potential functions with exponential repulsive interaction and explains the multi-body interaction between liquid helium atoms, in which the attractive part is the main part of the van der Waals attractive interaction. Another potential function with exponential repulsive interaction is the Bruch-McGee semi-empirical piecewise function, but its final expression and application is complex. Tang-Toennies potential function is more appropriate for describing the helium gas with low density. The dimensionless equations of the intermolecular force for helium-4 atoms are obtained based on the dimensional analysis and can be used in the molecular dynamics simulation.

Key words: helium, molecular dynamics, potential function, intermolecular interaction