Abstract:
In the article there were estimated the pair potential and pressure of bulk modules in molten systems. There
are given appropriate formulas for calculating the compressibility of electron melts. The polytherms of compressibility
for selenium, tellurium, germanium and silicon are calculated. For the calculation of bulk modules,
melts of metals and semiconductors are considered as a two-component liquid consisting of ions and
electrons. According to the virial theorem, a part of the pressure associated with the dynamics and interaction
of the ion subsystem is estimated. Since the isothermal bulk modulus is a static exponent, we determined it
under conditions where the pressure and volume in the system change slowly, and the temperature of the melt
changes very slowly or remains constant. The adiabatic bulk modulus, i.e. dynamic, was determined under
conditions of heating of the melt caused by compression. Under adiabatic compression a change in
temperature and pressure is allowed. This phenomenon occurs in fast processes, i.e. when there is no heat
exchange due to the inertia of the thermal properties of the melts. This behavior of adiabatic compressibility
is characteristic of metallic melts. We have found that the instantaneous dynamic modulus calculated in the
pair approximation model is identical to the dynamic modulus calculated in the full theory in the second order,
and also differs markedly from the statistical module. The explanation of this fact consists in neglecting
the members of the electron-ion interaction of a higher order than the second, and also the unsatisfactory
modification of the pseudopotential by means of an amendment to the Hartree energy. We obtained the relationships
that make possible to calculate the compressibility of melts. Theoretical calculated polytherms of
compressibility for semiconductors are given in the article.
