Compression behavior and structure of dense helium at high temperatures bymolecular dynamics simulation

In this work, the isotherm and energy distribution at T = 304 K of dense he lium are studied by molecular dynamic (MD) simulations with exp-6 potential r* = 2.967 3 Angstrom (the position of the well minimum) and epsilon/k(B) = 10.8 K (epsilon is the well-depth and k(B) is the Boltzmann constant) giv en by Peter et at., and different values of stiffness parameter alpha. The optimized value of alpha = 12.7 is deduced that can describe the atomic int eractions for dense helium satisfactorily. This optimized a in exp-6 potent ial is used to conduct MD simulations of two isotherms of dense helium at T = 300 K and T = 298 K. The calculations are in good agreement with the exp erimental. We further employed this method to investigate the equation-of-s tate and structure of dense helium at higher temperatures and found that wh en the density remained 1.6 g/cm(3), the second peak of the radial distribu tion function would disappear in the temperature range from 2 000 to 3 040 K, demonstrating that a solid-liquid transition or decrystallization had oc curred.