Theoretical Study On The Applicability Of Analytical Universal Equation Of State

In this article, the significance of equation of state (EOS) and the progress in isothermal EOS research are introduced at first. And then the mothods for determinding the parameters of isothermal EOS, including experimental and theoretical methods, semi-empirical and semi-theoretical methods, are comparatively comprehensive reviewed and analyzed. Based on the results mentioned above, two aspects of works are made.Four equations have been applied to fit the experimental compression data of 50 materials. The optimized values of bulk modulus and its first-order pressure derivative at zero pressure have been determined, and the average errors are compared. The results show that for all materials the Morse equation gives the best results,The BM, Vinet and Baonza equations subsequently give inferior results. For materials at wide pressure range, we recommend the Morse equation, but at middle and low pressure ranges, we recommend the Baonza equation as it can be expressed as both pressure analytic form and volume analytic form.We proposed a new EOS, and the new EOS can include the widely used Vinet EOS as special case. We applied the new EOS and the other universal EOS to 15 ionic solids and 32 metals. The calculated results show that the new EOS can not only give reasonable conhesive energy, but also fit the experimental compression data fairly good. In addition, the new EOS holds reasonable behavior both at high pressure and at expansion region.