First principle methods for calculating the linear coefficient of thermal expansion of quasi-binary eutectic systems


I. M. Frantsevich Institute for Problems of Materials Science of the NAS of Ukraine, Kyiv
Usp. materialozn. 2021, 3:38-47


To calculate the linear coefficient of thermal expansion (LCTE) and its temperature dependence, a combination of the method of a priori pseudopotential and quasiharmonic approximation (author's methods) is used. After approximating the results obtained for metal-like materials (carbides, borides, silicides), the LCTE is presented in an analytical form. In the case of quasi-binary eutectic systems based on carbides, borides, silicides, to estimate the interaction energy of the elements of two components, the concept of a virtual crystal (with a virtual cell) along the line of contact of two components is introduced. A virtual cell is assigned a volume average between the volume of a unit cell of two components, taking into account their concentration ratio. The components that make up the eutectic retain their crystal structure, their LCTE can be estimated as for pure components. Without taking into account the influence of interphase interaction, the LCTE of the eutectic system is determined using the rule of mixtures based on the LCTE components, taking into account their volume fraction. Taking into account the influence of the interface on thermal expansion is estimated by the virtual cell assigned to it. To determine the LCTE of the eutectic system, a ratio is proposed that connects the LCTE components and the docking boundaries through the concentration ratio. This method more realistically describes the structure of a quasibinary eutectic. There is a consistency between the calculated and experimental data

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