Theory of Compressibility of Simple Liquid Metals

Abstract

Pressure and compressibility of simple metals such as alkali metals, Zn, Al and Pb are calculated in the liquid state near the triple point, using the pseudopotential formalism for electron-ion interaction. Effective ion-ion interaction is defined naturally by calculating the total energy of metals to the second order of the electron-ion pseudopotential and its contributions to pressure and bulk modulus are calculated separately by the use of the so-called pressure equation of state modified properly to include the effects of the density-dependence (due to the electronic screening effect) of the effective ion-ion potential. It is found that these contributions are much larger (of more repulsive nature) than those estimated by using the Percus-Yevick solution for the hard-sphere model. The effects of the density dependence of the ion-ion interaction are found quite important for the pressure in alkali metals. Comparison of the calculated values of compressibility with experiments is made and the agreement is found satisfactory.