T(3) specific heat anomaly in network solids.
01 January 1985
A large T(3) specific heat anomaly associated with a vibrational mode near 40 cm(-1) is found in cristobalite and vitreous silica, but not in quartz or g-B2O3. A material-specific structural model is proposed for this anomaly. The model also explains the 40 and 80 cm(-1) modes observed by neutron scattering in cristobalite and g-SiO2 as well as the absence of dispersion in the hypersonic transverse sound velocity. Specific relations with recently observed anomalies in the 775 cm(-1) Raman band of mixed alkali silicates are suggested and specific experiments designed to test phase separation at the elemental molecular level (true spinodal decomposition) are proposed.