Pyroxene-ideal Thompson R M, Downs R T American Mineralogist 88 (2003) 653-666 Model pyroxenes I: Ideal pyroxene topologies Pyroxene #22b based on stacking sequence ABACBACBACBC Note: Atoms Mg, Si, and O are assigned to atomic positions just for convenience. _database_code_amcsd 0003029 19.595917 6 3.4641016 90 90. 90 P2_1/c atom x y z SiA 1/48 5/6 1/6 Mg1a 1/12 1/6 1/6 Mg2a 1/12 0 2/3 SiB 7/48 5/6 1/6 SiC 3/16 1/3 0 Mg1b .25 2/3 0 Mg2b .25 0 0 SiD 5/16 1/3 0 SiE 17/48 2/3 1/3 Mg1c 5/12 1/6 1/6 Mg2c 5/12 0 2/3 SiF 23/48 2/3 2/3 O1A 23/24 5/6 1/6 O2A 1/24 0 1/3 O3A 1/24 2/3 1/3 O1B 5/24 5/6 1/6 O2B 1/8 0 0 O3B 1/8 2/3 0 O1C 1/8 1/3 0 O2C 5/24 0 2/3 O3C 5/24 1/6 1/6 O1D 3/8 1/3 0 O2D 7/24 0 1/3 O3D 7/24 1/3 1/3 O1E 7/24 2/3 1/3 O2E 3/8 0 0 O3E 3/8 2/3 0 O1F 13/24 2/3 2/3 O2F 11/24 0 1/3 O3F 11/24 2/3 1/3