Pyroxene-ideal
Thompson R M, Downs R T
American Mineralogist 89 (2004) 614-628
Model pyroxenes II: Structural variation as a function of tetrahedral rotation
model with O3-O3-O3 angle = 160 and model oxygen radius = 1
Note: Atoms Mg, Si, and O are assigned to atomic positions for convenience
_database_code_amcsd 0003475
7.326 6.823 3.939 90 107.7 90 C2/c
atom     x      y      z
Mg1      0  11/12    1/4
Mg2      0    .25    1/4
Si   .3085   1/12  .2576
O1   .1330   1/12  .1585
O2   .3670    .25  .3415
O3   .3670  .0255  .0152