Quartz
Levien L, Prewitt C T, Weidner D J
American Mineralogist 65 (1980) 920-930
Structure and elastic properties of quartz at pressure
P = 37.6 kbar
_database_code_amcsd 0000791
4.7736 4.7736 5.301 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   .4581     0     0 0.0079 0.0068 0.0035 0.0034 -0.0005 -0.0010
O    .4079 .2867 .1039 0.0155 0.0123 0.0069 0.0075 -0.0040 -0.0032