Gruneisen constants for optical modes of α-quartz

Thermal expansion of the α-quartz lattice is compared to expansion induced by fast-neutron bombardment, on the basis of the relationship $∆ν_j/ν_j = = (-γ_j∆V)/V$, where $∆ν_j/ν_j$ is the change in the frequency of normal lattice vibration, ∆V/V is the crystal cubic expansion, $γ_j$ is the Gruneisen constant of the j-th normal lattice vibration (of frequency $ν_j$). It is shown that various normal vibrations introduce different contributions to expansion of the quartz lattice induced by heating or by fast-neutron bombardment.