Atomic Contribution to Crystalline Property Temperature Dependence

Abstract

General atomic locations in crystal structures are temperature dependent: the average thermal change in simple inorganic crystals is of the order of 10 - 3 A K - 1, with corresponding thermal coefficients of about 10 - 3 K - 1. A survey of the thermal coefficients for seven important crystal properties shows that these also have average values of about 10 - 3 K - 1, within one order of magnitude. Correlations between microscopic and macroscopic thermal dependence have been developed for the properties of spontaneous polarization and spontaneous strain. Comparable correlations are predicted for the case of piezoelectric strain. Scaling considerations suggest that the remaining dielectric, thermal and optical properties are similarly related to atomic location thermal coefficients. By contrast, the much smaller thermal dependence of such properties as expansivity and refractive index, with coefficients of about 10 - 5 K - 1, suggests that these properties are dominated by electronic rather than ionic interactions.