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 = 140 and model oxygen radius = 1
Note: Atoms Mg, Si, and O are assigned to atomic positions for convenience
_database_code_amcsd 0003476
7.023 6.510 3.759 90 104.1 90 C2/c
atom     x      y      z
Mg1      0  11/12    1/4
Mg2      0    .25    1/4
Si   .3100   1/12  .2248
O1   .1301   1/12  .1427
O2   .3699    .25  .3573
O3   .3699  .0525  .9497