Jun, 1998
Crystal chemical characteristics of alpha-CaSi2O5, a new high pressure calcium silicate with five-coordinated silicon synthesized at 1500 degrees C and 10 GPa
PHYSICS AND CHEMISTRY OF MINERALS
- ,
- Volume
- 25
- Number
- 6
- First page
- 429
- Last page
- 433
- Language
- English
- Publishing type
- DOI
- 10.1007/s002690050132
- Publisher
- SPRINGER VERLAG
The crystal structure of alpha-CaSi2O5 synthesized at conditions of 1500 degrees C and 10 GPa, has been solved and refined in centrosymmetric space group P (1) over bar, using single crystal X-ray diffraction data. The composition (Z=4) and unit cell are Ca1.02Si1.99O5 by EPMA analysis and a=7.243(2) Angstrom, b=7.546(4) Angstrom, c=6.501(4) Angstrom, alpha=81.43(5)degrees, beta=84.82(4)degrees, gamma=69.60(3)degrees, V=329.5(3) Angstrom(3), yielding the density value, 3.55 g/cm(3). The structure is closely related to that of titanite, CaTiSiO5 and features the square-pyramid five-fold coordination of silicon by oxygen. The ionic radius for five-coordinated Si calculated from the bond distances is 0.33 Angstrom. The substantial deviation of valence sum for Ca indicates the existence of local strain and the instability of alpha-CaSi2O5 at room pressure.
- Link information
- ID information
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- DOI : 10.1007/s002690050132
- ISSN : 0342-1791
- Web of Science ID : WOS:000074814500003