Quantum-mechanical approach to simulation of molecular crystals thermal conductivity

Abstract

This article is devoted to the implementation of scientific achievements into the educational process of physics specialties students in the framework of study course “Solid State Physics”. In this work, based on our previous scientific results, we present a quantum-mechanical approach that can adequately describe the temperature dependences of the dielectric crystals thermal conductivity. The basic provisions of quantum-mechanical approach are studied by students in the framework of university study course “Solid State Physics” and are based on Einstein and Debye classical models. This approach is based on the assumption that in dielectric crystals heat is transferred due to the phonons (Debye model) and thermal diffusion between the thermally activated neighboring quantum mechanical oscillators directly from site to site on a time scale of one-half of the oscillation period (Einstein model). In term of this consideration the thermal conductivity of molecular crystals are simulated in the framework of thermal conductivity model where heat is transferred by low-frequency phonons with taking into account phonon–rotation coupling, and above the phonon mobility edge by “diffusive” modes. For this purpose the theoretical temperature dependences of the isochoric thermal conductivity have been calculated numerically in the interval near or over the Debye temperature and compared with experimental results for solid C6H12, CHCl3 and CH2Cl2. Using simple molecular crystals as an example it is shows the dualism of the nature of heat transfer processes in the temperature region of the order of the Debye temperature and above. The obtained results will be useful for implementation in the educational process in the study course “Solid State Physics” in particular for understanding the features of heat transfer in the high-temperature range of dielectric crystals existence.