Quartz
Levien L, Prewitt C T, Weidner D J
American Mineralogist 65 (1980) 920-930
Structure and elastic properties of quartz at pressure
P = 55.8 kbar
_database_code_amcsd 0000793
4.722 4.722 5.267 90 90 120 *P3_221
0 0 .666666667
atom     x     y     z B(1,1) B(2,2) B(3,3) B(1,2)  B(1,3)  B(2,3)
Si   .4537     0     0 0.0082 0.0074 0.0036 0.0037 -0.0002 -0.0004
O    .4047 .2926 .0998 0.0153 0.0117 0.0062 0.0079 -0.0032 -0.0030