Optimization of heat capacities of wurtzite phases as a single system and thermodynamic properties of nihonium nitride

Vassiliev, V.P.; Stanley, C.M.

Авторы: Vassiliev V.P., Stanley C.M.
Журнал: Calphad: Computer Coupling of Phase Diagrams and Thermochemistry
Том: 89
Год издания: 2025
Издательство: Pergamon Press Ltd.
Местоположение издательства: United Kingdom
Первая страница: 1
Последняя страница: 31
Номер статьи: 102824
DOI: 10.1016/j.calphad.2025.102824
Аннотация: In this work, two independent methods were used to describe the heat capacity of reference compounds with thewurtzite structure, as well as their isostructural analogs of fourth group elements in the solid state: 1) a semiempirical method using a multiparameter function and 2) a method based on the density functional theory. Inthe first method, to describe a set of isostructural experimental data Cp(T) of substances in the solid state, adescription of each individual phase was carried out in the first approximation, and then, after finding a set of itsfitting parameters (X), a description of the entire set of data as an integral system, where the set of each individual fitting parameter was described by a polynomial equation of functions included in the multiparameterfamily with the best description of the set of all data. The parameters of unexplored substances were found byinterpolation of the multiparameter function. The fitting parameters (X) are a function of the atomic number ofthe elements Si, Ge, Sn, Pb, and Fl or the half-sum of the atomic numbers of the binary phases AIIIBV: B, Al, Ga, Tl,and Nh with the element germanium having a characteristic point for the set of parameters (X) depending on theatomic number. For each substance, the parameters are found by minimizing the discrepancy between thetheoretical dependence Cp(T) and the corresponding experimental data. According to the fine structure constant(α = 1/137) (or Sommerfeld constant), there are no other elements in this group. Therefore, the limiting heatcapacity of the wurtzite phases is at element 114 (114Fl) and has a value of Cp = 30.5 ± 0.3 J ⋅ mol-at− 1 ⋅ K− 1.The second method allows us to describe the heat capacities (Cp) for these materials using a new first principles method based on the density functional theory. This method, called the Beyond Quasi-Harmonicmethod, includes all anharmonic vibrations - volume changes and phonon-phonon interactions. Our calculated values for III-V compounds with wurtzite and sphalerite structures show good agreement between the twomethods.This work also presents optimized thermodynamic properties, Gibb’s energy, enthalpy and entropy of formations, as well as standard entropy and melting point of III-V nitrides, including nihonium nitrid
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Optimization of heat capacities of wurtzite phases as a single system and thermodynamic properties of nihonium nitrideстатья

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