Pyroxene-ideal
Thompson R M, Downs R T
American Mineralogist 88 (2003) 653-666
Model pyroxenes I: Ideal pyroxene topologies
Pyroxene #17a based on stacking sequence ABABACACBCBC
Note: Atoms Mg, Si, and O are assigned to atomic positions just for convenience.
_database_code_amcsd 0003019
19.595917 6 3.4641016 90 90. 90 P2/c
atom    x    y     z
Mg1a    0 5/12   1/4
Mg2a    0  .25   3/4
SiA  1/16 1/12  7/12
SiB  5/48 7/12  5/12
Mg1b  1/6 1/12 11/12
Mg2b  1/6  .25  5/12
SiC 11/48 7/12  1/12
SiD 13/48 1/12   1/4
Mg1c  1/3 5/12 11/12
Mg2c  1/3  .25  5/12
SiE 19/48 1/12  7/12
SiF  7/16 5/12   1/4
Mg1d  1/2 1/12   1/4
Mg2d  1/2  .25   3/4
O1A   1/8 1/12  7/12
O2A  1/24  .25  5/12
O3A  1/24 1/12 11/12
O1B  1/24 7/12  5/12
O2B   1/8  .25  1/12
O3B   1/8 7/12  1/12
O1C  7/24 7/12  1/12
O2C  5/24  3/4   1/4
O3C  5/24 5/12   1/4
O1D  5/24 1/12   1/4
O2D  7/24  .25  1/12
O3D  7/24 1/12  7/12
O1E 11/24 1/12  7/12
O2E   3/8  .25   3/4
O3E   3/8 1/12   1/4
O1F   3/8 5/12   1/4
O2F 11/24  .25  1/12
O3F 11/24 7/12  1/12