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Electron and nuclear pressures in electron-nucleus mixtures
It is shown for an electron-nucleus mixture that the electron and nuclear
pressures are defined clearly and simply by the virial theorem; the total
pressure of this system is a sum of these two pressures. The electron pressure
is different from the conventional electron pressure being expressed as the sum
of two times of kinetic energy and the potential energy in that the nuclear
virial term is subtracted; this fact is exemplified by several kinds of
definitions for the electron pressure enumerated in this work. The conventional
definition of the electron pressure in terms of the nuclear virial term is
shown inappropriate. Similar remarks are made about the definition of the
stress tensor in this mixture. It is also demonstrated that both of the
electron and nuclear pressures become zero at the same time for a metal in the
vacuum, in contrast to the conventional viewpoint that the zero pressure is
realized by a result of the cancellation between the electron and nuclear
pressures, each of which is not zero. On the basis of these facts, a simple
equation of states for liquid metals is derived, and examined numerically for
liquid alkaline metals by use of the quantum hypernetted chain equation and the
Ashcroft model potential.Comment: 24pages. 2 ps-figures, use epsf.sty, namelist.sty,REVtex macro
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