Pyroxene-ideal
Thompson R M, Downs R T
American Mineralogist 88 (2003) 653-666
Model pyroxenes I: Ideal pyroxene topologies
Pyroxene #12a based on stacking sequence ABABABABCBAC
Note: Atoms Mg, Si, and O are assigned to atomic positions just for convenience.
_database_code_amcsd 0003011
19.595917 6 3.4641016 90 90. 90 P2/c
atom    x     y     z
SiA  1/16  7/12  5/12
SiB  5/48  1/12  7/12
SiC 11/48  1/12 11/12
SiD 13/48  5/12  7/12
SiE 19/48  7/12  5/12
SiF  7/16  1/12   1/4
Mg1a    0  1/12   1/4
Mg2a    0   .25   3/4
Mg1b  1/6  5/12   1/4
Mg2b  1/6   .25   3/4
Mg1c  1/3  1/12  7/12
Mg2c  1/3   .25  1/12
Mg1d  1/2  5/12   1/4
Mg2d  1/2   .25   3/4
O1A   1/8  7/12  5/12
O2A  1/24   3/4  7/12
O3A  1/24  5/12  7/12
O1B  1/24  1/12  7/12
O2B   1/8   .25  5/12
O3B   1/8  1/12 11/12
O1C  7/24  1/12 11/12
O2C  5/24   .25  1/12
O3C  5/24  1/12  7/12
O1D  5/24  5/12  7/12
O2D  7/24   .25  5/12
O3D  7/24  7/12  5/12
O1E 11/24  7/12  5/12
O2E   3/8   .25   3/4
O3E   3/8  7/12   3/4
O1F   3/8  1/12   1/4
O2F 11/24   .25  5/12
O3F 11/24 11/12  5/12