Verification of ideal dense matter equation of state by molecular dynamics simulation

Abstract

Equation of state (EOS) of dense matter has a wide application in geophysics, astrophysics, and physical detonation. However, it is difficult to obtain simple and accurate EOS under ultrahigh-density conditions due to the complex matter structures. Recently, an ideal dense matter EOS based on thermodynamic symmetry has been proposed for ultrahigh-density matter, which is symmetric to ideal gas EOS. Here, owing to experimental limitations, molecular dynamics (MD) is performed to verify the EOS. First, we discuss the feasibility of a thermodynamic integration algorithm for implementing an isentropic process at ultrahigh density. Second, by analogy with heat capacity, we clarify that work capacity reflects the ability of matter to do work. Theoretical analysis shows that internal energy and work capacity of ideal dense matter are independent of temperature. Furthermore, MD simulations demonstrate that the effect of temperature on internal energy and work capacity weakens with increasing density, which conforms to the inference of ideal dense matter EOS. Finally, by simulating isentropic, isothermal, isobaric, and isochoric processes, it is found that the accuracy of ideal dense matter EOS in describing thermodynamic properties is positively related to the density. It is another perspective for the understanding of dense matter and ultrahigh-density EOS.