Thermal Expansion of Some Crystals with the Diamond Structure

The linear coefficient of thermal expansion of silicon, germanium, and indium antimonide has been measured in the range 4.2°K-300°K using an interferometric method. In the cases of silicon and germanium, these values are used to calculate the variation in Grüneisen's factor $\gamma$ with temperature and the result is compared with the predictions of T. H. K. Barron. Silicon and indium antimonide have negative values for $\gamma$ at low temperatures and some of the requirements for a structure to behave in this manner are suggested, namely, fourfold coordination in the lattice, covalent bonding, and openness of structure.