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The 6H-SiC structure model; further refinement from SCXRD data from a terrestrial moissanite

Gian Carlo Capitani, Simonpietro Di Pierro and Gioacchino Tempesta
The 6H-SiC structure model; further refinement from SCXRD data from a terrestrial moissanite (in Microbeam cathodoluminescence, Ian M. Coulson (prefacer), Paul R. Edwards (prefacer) and Martin R. Lee (prefacer))
American Mineralogist (February 2007) 92 (2-3): 403-407


The crystal structure of a terrestrial 6H-SiC moissanite has been refined in the P6 (sub 3) mc S.G. from area detector single crystal X-ray data, down to an R-index on the observed reflections of 0.0205. The cell parameters refined over all the collected reflections are a = 3.0810(2) and c = 15.1248(10) Aa. The average Si-C bond lengths are 1.8898 Aa, with average bonds along the stacking direction (1.8993 Aa) slightly longer than those along the bilayer (1.8862 Aa). The interlayer distances, defined as the distances along [0001] between Si-Si layers, which may occur either in cubic (c) or hexagonal (h) configurations, are maximal at the c-h interface (2.5270 Aa) and minimal at the h-c interface (2.5165 Aa), entailing that the h-bilayer is not equidistant from either c-bilayers. All the tetrahedral angles are identical within the experimental error and close to the ideal value of 109.47 degrees , but those at the c-h interface, where a significant distortion of 0.15 degrees is recorded. Finally, the anisotropic displacement factors are utterly very small, identical among different atoms within the experimental error, and significantly spherical. It thus appears that the 6H-SiC structure is affected by a slight relaxation along the [0001] stacking direction with respect to the ideal cubic structure, and that the relaxation is mainly accomplished at the c-h interface, i.e., at the twin-like boundary, where a bilayer in cubic configuration links a bilayer in antiparallel, hexagonal configuration. As far as we know this is the first crystal structure refinement of a natural 6H-SiC moissanite. Possible implications on the polytype stability in the light of these results are briefly discussed.

ISSN: 0003-004X
EISSN: 1945-3027
Serial Title: American Mineralogist
Serial Volume: 92
Serial Issue: 2-3
Title: The 6H-SiC structure model; further refinement from SCXRD data from a terrestrial moissanite
Title: Microbeam cathodoluminescence
Author(s): Capitani, Gian CarloDi Pierro, SimonpietroTempesta, Gioacchino
Author(s): Coulson, Ian M.prefacer
Author(s): Edwards, Paul R.prefacer
Author(s): Lee, Martin R.prefacer
Affiliation: Universita di Bari, Dipartimento Geomineralogico, Bari, Italy
Affiliation: University of Regina, Department of Geology, Regina, SK, Canada
Pages: 403-407
Published: 200702
Text Language: English
Publisher: Mineralogical Society of America, Washington, DC, United States
References: 35
Accession Number: 2007-039042
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 4 tables
Secondary Affiliation: University of Strathclyde, GBR, United KingdomUniversity of Glasgow, GBR, United KingdomEcole Normale Superieure de Lyon, FRA, France
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Mineralogical Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 200721
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