Crystal structure and thermal expansion of α‐quartz SiO2 at low temperatures

✍ Scribed by Lager, G. A.; Jorgensen, J. D.; Rotella, F. J.

• Book ID: 115543772
• Publisher: American Institute of Physics
• Year: 1982
• Tongue: English
• Weight: 584 KB
• Volume: 53
• Category: Article
• ISSN: 0021-8979
• DOI: 10.1063/1.330062

✦ Synopsis

The crystal structure of α-SiO2 (low quartz) has been refined at 296, 78, and 13 K from time-of-flight neutron powder diffraction data. The major effect of temperature from 296 to 78 K is a nearly rigid body rotation of the SiO4 tetrahedra. Below 78 K, tetrahedral rotation is substantially reduced giving rise to a much smaller thermal expansion. A comparison of the volume dependence of the Si-O-Si angle, the rotation angle for SiO4 tetrahedra and the c/a ratio suggests that the mechanism for expansion may be changing from tetrahedral rotation to tetrahedral distortion at the lowest temperatures. The inverse linear relation between the mean Si-O bond distance and −sec(Si-O-Si) which has been observed for silica minerals at both ambient and high-temperature conditions appears to be consistent with the structural variations that occur at low temperatures.