Pyroxene-ideal
Thompson R M, Downs R T
American Mineralogist 88 (2003) 653-666
Model pyroxenes I: Ideal pyroxene topologies
Pyroxene #19a based on stacking sequence ABABCABCBCAC
Note: Atoms Mg, Si, and O are assigned to atomic positions just for convenience.
_database_code_amcsd 0003022
19.595917 6 3.4641016 90 90. 90 P2_1/c
atom    x   y   z
SiA  1/48 1/3 1/3
Mg1a 1/12 2/3 1/3
Mg2a 1/12 1/2 5/6
SiB  7/48 1/3 1/3
SiC  3/16 2/3   0
Mg1b  .25 1/6 1/6
Mg2b  .25   0 2/3
SiD  5/16 2/3 1/3
SiE 17/48 1/3   0
Mg1c 5/12 2/3   0
Mg2c 5/12   0   0
SiF 23/48 1/3 1/3
O1A 23/24 1/3 1/3
O2A  1/24   0 2/3
O3A  1/24 1/3 2/3
O1B  5/24 1/3 1/3
O2B   1/8   0   0
O3B   1/8 1/6 1/2
O1C   1/8 2/3   0
O2C  5/24   0 1/3
O3C  5/24 2/3 1/3
O1D   3/8 2/3 1/3
O2D  7/24   0   0
O3D  7/24 2/3   0
O1E  7/24 1/3   0
O2E   3/8   0 1/3
O3E   3/8 1/3 1/3
O1F 13/24 1/3 1/3
O2F 11/24   0 2/3
O3F 11/24 1/3 2/3