Pyroxene-ideal
      Thompson R M, Downs R T
      American Mineralogist 88 (2003) 653-666
      Model pyroxenes I: Ideal pyroxene topologies
      Pyroxene #2 based on stacking sequence ABAC. Ideal analogue of  protopyroxene,
      high-P protopyroxene.
      Note: Atoms Mg, Si, and O are assigned to atomic positions just for convenience.
      _database_code_amcsd 0002997

      CELL PARAMETERS:    6.5320   6.0000   3.4641   90.000   90.000   90.000
      SPACE GROUP: P2_1cn    
      X-RAY WAVELENGTH:     1.541838
      Cell Volume:    135.764
      Density (g/cm3):      9.821
      MAX. ABS. INTENSITY / VOLUME**2:      17.30587328    
      RIR:      0.574
      RIR based on corundum from Acta Crystallographica A38 (1982) 733-739
               2-THETA      INTENSITY    D-SPACING   H   K   L   Multiplicity
                20.10          1.26        4.4188    1   1   0         2
                27.31          4.25        3.2660    2   0   0         1
                29.78          9.02        3.0000    0   2   0         2
                29.78         12.75        3.0000    0   1   1         4
                32.85         17.93        2.7262    1   1   1         4
                40.84         29.77        2.2094    2   2   0         2
                40.84         12.65        2.2094    2   1   1         4
                42.18         70.58        2.1423    1   2   1         4
                44.25         98.26        2.0467    3   1   0         2
                48.89         43.77        1.8628    2   2   1         4
                51.89         13.55        1.7621    3   1   1         4
                52.86          1.17        1.7321    0   3   1         4
                54.84         66.67        1.6742    1   3   1         4
                54.84         33.33        1.6742    1   0   2         2
                56.34          4.50        1.6330    4   0   0         1
                57.12         26.92        1.6126    1   1   2         4
                58.79          3.50        1.5706    3   2   1         4
                60.50         31.00        1.5302    2   3   1         4
                60.50         15.50        1.5302    2   0   2         2
                61.85          1.30        1.5000    0   2   2         4
                62.66         19.17        1.4827    2   1   2         4
                63.65          2.22        1.4619    1   2   2         4
                65.03          6.21        1.4343    4   1   1         4
                68.88          5.42        1.3631    2   4   0         2
                68.88          2.40        1.3631    2   2   2         4
                69.33         18.08        1.3555    3   3   1         4
                69.33          9.04        1.3555    3   0   2         2
                69.83         14.03        1.3469    1   4   1         4
                71.15          7.35        1.3252    4   2   1         4
                71.33          1.90        1.3222    3   1   2         4
                74.30          2.64        1.2765    5   1   0         2
                74.86         10.54        1.2684    2   4   1         4
                77.23          3.58        1.2352    3   2   2         4
                80.91         21.61        1.1882    4   3   1         4
                80.91         10.81        1.1882    4   0   2         2
                82.82          4.56        1.1655    4   1   2         4
                83.00          1.23        1.1635    3   4   1         4
                85.85          3.60        1.1320    5   2   1         4
                88.51          2.52        1.1047    4   2   2         4
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       XPOW Copyright 1993 Bob Downs, Ranjini Swaminathan and Kurt Bartelmehs
  For reference, see Downs et al. (1993) American Mineralogist 78, 1104-1107.