Diamond's elastic stiffnesses from 322 K to 10 K

Using resonant-ultrasound spectroscopy, we measured diamond's monocrystal elastic-stiffness coefficients C-11, C-12, and C-44, between 322 and 10 K. Changes are small and smooth: The bulk modulus B=(C-11+2C(12))/3 increases about 1 part in 1000, describable by a quasiharmonic Einstein-oscillator model. Zero-temperature C-ij correspond to a 2244-K Debye characteristic temperature. Using a low-temperature form of the Gruneisen-Debye model, we calculated an overall thermodynamic Graneisen parameter of gamma=1.26; using a high-temperature form we calculated 0.71; the lattice specific heat yields gamma=1.10. (C) 2008 American Institute of Physics.