A New Fourth Order Compression Dependent Equation of State

Abstract

This study introduces a new first- to fourth-order exponential equation of state (EOS) to enhance accuracy across varying compression levels. The proposed exponential EOS is compared to the widely used fourth-order Birch-Murnaghan EOS, and it not only matches but surpasses precision, especially at high compression. This comparison serves as a clear benchmark for the readers to understand the superiority of the new model. The findings of this study are crucial, as they reveal that the fourth-order exponential EOS provides an unmatched accuracy level at higher compression, notably for materials like HCP-iron and sodium halides. The Birch-Murnaghan EOS, though effective at low compression, deviates from experimental values at higher levels. Additionally, the study examines the Shanker EOS, in which M. Kumar et al. [Physica B: Condensed Matter, 239(3-4), 337-344 (1997)] suggest the requirement to improve at high compression and improve by fitting parameters that vary from material to material. This limitation is removed by developing the fourth-order exponential EOS, which is more versatile, offering reliable results across both low- and high-compression scenarios in high-pressure physics.

Keywords

• equation of state, compression, fourth-order exponential equation of state, birch-murnaghan fourth-order equation of state.