Condensed-matter equation of states covering a wide region of pressure studied experimentally

TL;DR

This paper introduces a simple cubic polynomial empirical equation of state that accurately models the pressure-volume relationship of condensed matter across a wide pressure range, including phase transitions.

Contribution

The study presents a new empirical EOS with three parameters that effectively describes experimental P-V data over broad pressure ranges, surpassing previous models.

Findings

Accurately fits experimental P-V data across wide pressure ranges.

Works well even with phase transitions present.

Provides a simple mathematical form for EOS modeling.

Abstract

The relationships among the pressure P, volume V, and temperature T of solid-state materials are described by their equations of state (EOSs), which are often derived from the consideration of the finite-strain energy or the interatomic potential.1-3 These EOSs consist of typically three parameters to determine from experimental P-V-T data by fitting analyses. In the empirical approach to EOSs, one either refines such fitting parameters or improves the mathematical functions3-5 to better simulate the experimental data. Despite over seven decades of studies on EOSs, none has been found to be accurate for all types of solids over the whole temperature and pressure ranges studied experimentally.3,6,7 Here we show that the simple empirical EOS, P = {\alpha}1(PV) + {\alpha}2(PV)2 + {\alpha}3(PV)3, in which the pressure P is indirectly related to the volume V through a cubic polynomial of the energy term PV with three fitting parameters {\alpha}1 - {\alpha}3, provides accurate descriptions for the P-vs-V data of condensed matter in a wide region of pressure studied experimentally even in the presence of phase transitions