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 protopyroxene after Yang et al. (1999)
with O3-O3-O3 angle = 165.9 and model oxygen radius = 1.306
Note: Atoms Mg, Si, and O are assigned to atomic positions for convenience
_database_code_amcsd 0003523
9.154 8.981 5.185 90 90 90 Pbcn
atom     x      y      z
Mg       0   1/12    3/4
Mg       0    .25    1/4
Si   .3082   1/12   1/12
O1   .1335   1/12   1/12
O2   .3665    .25  .1191
O3   .3665 -.0179  .3155