Study of the Anomalous Thermodynamic Properties of the LaCoO 3 System Based on the Pseudocubic Approximation

— The thermodynamic properties of the LaCoO 3 system, namely, the specific heat, the thermal-expansion coefficient, and the Grüneisen parameter, are studied using a phenomenological pseudocubic model. The validity of the pseudocubic approximation is confirmed by the quantitative analysis of interatomic distances. The model is based on experimental data on the density of phonon states; in this case, the parameters of the force interatomic interaction are specified by the Born von Karman method and are given in Table 1. The lattice contribution to the specific heat up to 1000 K is calculated using the model. The anomalous contribution to the LaCoO 3 specific heat is estimated in the temperature range of 0–1000 K. The temperature dependence of the Grüneisen parameter of the anomalous contribution to the LaCoO 3 thermal-expansion coefficient was obtained in the temperature range of 0–200 K for the first time.