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

In this work, the isotherm and energy distribution atT= 304 K of dense helium are studied by molecular dynamic (MD) simulations with exp-6 potential r^* = 2.967 3 á (the position of the weil minimum) and ɛ/k _B = 10.8 K (ɛ is the well-depth andk _B is the Boltzmann constant) given by Peter et al., and different values of stiffness parameter α. The optimized value of α= 12.7 is deduced that can describe the atomic interactions for dense helium satisfactorily. This optimized α in exp-6 potential is used to conduct MD simulations of two isotherms of dense helium atT= 300 K andT = 298 K. The calculations are in good agreement with the experimental. We further employed this method to investigate the equation-of-state and structure of dense helium at higher temperatures and found that when the density remained 1.6 g/cm³, the second peak of the radial distribution function would disappear in the temperature range from 2 000 to 3 040 K, demonstrating that a solid-liquid transition or decrystallization had occurred.