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Funct. Mater. 2019; 26 (4): 807-815.

doi:https://doi.org/10.15407/fm26.04.807

Phase transitions in crystals: the electronic subsystem contribution

A.D.Suprun, V.V.Datsyuk, L.V.Shmeleva, S.M.Yezhov

Faculty of Physics, T.Shevchenko National University of Kyiv, 64/13 Volodymyrska Street, Kyiv, 01601, Ukraine

Abstract: 

The base energy of the electron subsystem of a condensed matter of a crystalline type was considered by quantum field theory methods. Here we considered monatomic condensates, because they are most simple from the point of view of the objects quantum description. In particular, evaluations were carried out for boron and the electronic subsystem was only taken into account. The exact value of the crystal internal energy as a function of temperature is obtained, and this dependence is completely determined by the Fermi-Dirac factor. Internal energy, as a function of this factor, has a sufficiently simple (parabolic) form. It is shown that the matrix elements included in the coefficients of this dependence are divided into two groups: centrally symmetric and anisotropic. Centrally symmetric matrix elements determine isotropic interactions. Such interactions are characteristic of liquids. Anisotropic matrix elements determine the interactions characteristic to crystals. It is shown that competition between them result in the phase transitions. The possibilities of analytical estimates for the contributions due to the electronic subsystem to the liquid-gas and crystal-liquid phase transition temperatures are analyzed.

Keywords: 
electronic subsystem, phase transitions, Fermi-Dirac factor.
References: 

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