Lattice vacancies responsible for the linear dependence of the low-temperature heat capacity of insulating materials

Article

关键词: OXYGEN-VACANCIES;    THERMODYNAMIC FUNCTIONS;    1ST-PRINCIPLES CALCULATIONS;    MAGNETIC-SUSCEPTIBILITY;    TIO2 ANATASE;    RUTILE TIO2;    DEFECTS;    NONSTOICHIOMETRY;    TERM;    YBA2CU3O7-DELTA;   

DOI  :  10.1103/PhysRevB.91.024109

来源: SCIE

【 摘 要 】

The linear dependence on temperature (gamma T) of the heat capacity at lowtemperatures (T < 15 K) is traditionally attributed to conduction electrons in metals; however, many insulators also exhibit a linear dependence that has been attributed to a variety of other physical properties. The property most commonly used to justify the presence of this linear dependence is lattice vacancies, but a correlation between these two properties has never been shown, to our knowledge. We have devised a theory that justifies a linear heat capacity as a result of lattice vacancies, and we provide measured values and data from the literature to support our arguments. We postulate that many small Schottky anomalies are produced by a puckering of the lattice around these vacancies, and variations in the lattice caused by position or proximity to some form of structure result in a distribution of Schottky anomalies with different energies. We present a mathematical model to describe these anomalies and their distribution based on literature data that ultimately results in a linear heat capacity. From these calculations, a quantitative relationship between the linear term and the concentration of lattice vacancies is identified, and we verify these calculations using values of gamma and vacancy concentrations for several materials. We have compiled many values of gamma and vacancy concentrations from the literature which show several significant trends that provide further evidence for our theory.

【 授权许可】

Free