Pyroxene-ideal
Thompson R M, Downs R T
American Mineralogist 88 (2003) 653-666
Model pyroxenes I: Ideal pyroxene topologies
Pyroxene #9a based on stacking sequence ABABCBAC
Note: Atoms Mg, Si, and O are assigned to atomic positions just for convenience.
_database_code_amcsd 0003006
13.063948 6 3.4641016 90 90. 90 P2/c
atom    x     y     z
SiA 29/32 11/12  1/12
SiB 27/32  5/12 11/12
SiC 13/32 11/12   3/4
SiD 11/32  7/12  5/12
Mg1a    0  5/12   1/4
Mg2a    0   .25   3/4
Mg1b  .25 11/12  1/12
Mg2b  .25   .25  1/12
Mg1c  1/2  7/12   3/4
Mg2c  1/2   .25   3/4
O1A 13/16 11/12  1/12
O2A 15/16   3/4 11/12
O3A 15/16  1/12 11/12
O1B 15/16  5/12 11/12
O2B 13/16   .25  1/12
O3B 13/16  7/12  1/12
O1C  5/16 11/12   3/4
O2C  7/16   3/4 11/12
O3C  7/16  1/12 11/12
O1D  7/16  7/12  5/12
O2D  5/16   3/4   1/4
O3D  5/16  7/12   3/4