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Crystal structure and optical spectroscopy (300 to 2200 nm) of CaCrSi_4O_(10)

Belsky, Howard L. and Rossman, George R. and Prewitt, Charles T. and Gasparik, Tibor (1984) Crystal structure and optical spectroscopy (300 to 2200 nm) of CaCrSi_4O_(10). American Mineralogist, 69 (7-8). pp. 771-776. ISSN 0003-004X.

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Crystals of CaCr^(2+)Si_4O_(10) were synthesized at 1 atm and 1400-1350°C in a closed system with fO_2 < 10^(-16) bar. CaCrSi_4O_(10) crystallizes in the space group P4/ncc with a= 7.378(5)Å and c = 15.119(2)Å. The structure was refined to R = 0.026 (R_w = 0.031) based on 546 reflections. CaCrSi_4O_(10) is a structural analog of gillespite and other ABSi_4O_(10) compounds, and although not itself a mineral, has been shown to exhibit structural and compression properties nearly identical to those of gillespite. The most interesting aspects of the structure are the square-planar coordination of Cr^(2+), and the Si-Ol-Si bond angle of 176.8°. Apparently, Cr^(2+) is stable in the gillespite structure because it is readily accepted into the square-planar site, in contrast to other C^(2+) compounds that are distorted from typestructures as a result of the Jahn-Teller effect in C^(2+). The optical absorption spectrum of CaCrS_4O_(10) has bands at 511 and 670 nm polarized ⊥ c and at 453 nm ‖ c, with all absorption occuring only through vibronic coupling. Diamond cell experiments indicate that CaCrSi_4O_(10) remains tetragonal to at least 50 kbar, with compression behavior identical to that of gillespite.

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Rossman, George R.0000-0002-4571-6884
Additional Information:© 1984 Mineralogical Society of America. Manuscript received, April 6, 1983; accepted for publication, January 31, 1984. The authors would like to express their thanks to Dr. Satoshi Sasaki and Mr. Ken Baldwin for assistance with X-ray and computer facilities. Figure 1 was expertly drafted by Ms. Lois Koh. Dr. Robert Hazen and Dr. Roger Burns provided critical readings of the manuscript. This research was supported in part by NSF Grant EAR81-20950.
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Issue or Number:7-8
Record Number:CaltechAUTHORS:20130514-092708645
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Official Citation: Howard L. Belsky, George R. Rossman, Charles T. Prewitt, and Tibor Gasparik Crystal structure and optical spectroscopy (300-2200nm) of CaCrSi4O10 American Mineralogist, August 1984, v. 69, p. 771-776
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:38481
Deposited By: Ruth Sustaita
Deposited On:14 May 2013 16:46
Last Modified:26 Nov 2019 11:15

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