The phonon heat capacity of diborides: The approximation of interacting sublattices

The temperature dependence of the heat capacity of structures formed by alternating layers with different atomic compositions is described using the model of interacting three- and two-dimensional Debye sublattices. The parameters of the model are the characteristic temperatures Θ₁ and Θ₃ of the sublattices and the characteristic temperature Θ₂ corresponding to vibrations between the sublattices. (In the accepted approximation, Θ₂ equals the characteristic Debye temperature of the substance at absolute zero.) The model was used to analyze the temperature dependences of the lattice (phonon) heat capacities of transition and rare-earth metal diborides MB₂. This allowed the characteristic temperatures Θ _i and trends of their variations depending on metal atomic numbers to be determined.