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 acmite after Cameron et al. (1973)
with O3-O3-O3 angle = 174.0 and model oxygen radius = 1.302
_database_code_amcsd 0003497
9.737 9.009 5.201 90 109.9 90 C2/c
atom     x      y      z
Fe       0  11/12    1/4
Na       0    .25    1/4
Si   .3081   1/12  .2794
O1   .1339   1/12  .1685
O2   .3661    .25  .3315
O3   .3661  .0076  .0587