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Analysis of high pressure equation of state for NaCl

J.Chandra, M.Mathpal, K.Kholiya, B.R.K.Gupta

Asimple theoreticalmodel is developed to study the high pressure behavior of solids and then applied to evaluate the pressure for compression below0.65 incase ofNaCl.Some otherwell known equation of states reported in the literature has also been included in the study. The comparison of calculated values fromall these equation of statewith experimen- INTRODUCTION The behavior of solids under the effectof high pressure has truly developed into an interdisciplinary area which has important implications for an application in the area of physics, biology, engineering and technology apart fromthe discovery of various novel and unexpected phenomenon, high pressure research has providednewinsight intothebehaviorofmatter[1].Strength and elastic properties of a solid depend on the strength of its interatomic forces. Therefore, the application of pressurewhich changes the interatomic distance of the substances changes its physical properties. The EOS gives usvaluable information about the relationship between the change in thermodynamic variable viz. pressure, volume and temperature. Every thermodynamic system has its own EOS, independent of others.An EOS expresses the peculiar behavior of one individual systemwhich distinguishes it fromthe others. In order to determine the EOS of a system, the thermodynamic variables of the system, are accuratelymeasured and a relation is expressedbetween them.TheEOSof a solid can be used as pressure gauge in high pressuremeasurements. Attempts have beenmade to derive a compressibilityequationfrommolecular theory, butnone of themhas resultedin convenient equationexpressingthe results of experimentswith adequate accuracy.Tomeet thisneedsome empirical equationshavebeenproposed, the sole justification ofwhich is that itworks. In spite of impressive advances on the theoretical front over the tal values reveals that the presentmodel yields the best agreement. The present study also shows that it is a good approximation to consider the pressure to be quadratic in the density