Pyroxene-ideal
      Thompson R M, Downs R T
      American Mineralogist 88 (2003) 653-666
      Model pyroxenes I: Ideal pyroxene topologies
      Pyroxene #1 based on HCP stacking sequence ABAB. Has the bonding topology of
      observed HT-C2/c pyroxenes.
      Note: Atoms Mg, Si, and O are assigned to atomic positions just for convenience.
      _database_code_amcsd 0002996

      CELL PARAMETERS:    7.3937   6.0000   3.4641   90.000  117.938   90.000
      SPACE GROUP: C2/c      
      X-RAY WAVELENGTH:     1.541838
      Cell Volume:    135.764
      Density (g/cm3):      9.821
      MAX. ABS. INTENSITY / VOLUME**2:      24.03049681    
      RIR:      0.797
      RIR based on corundum from Acta Crystallographica A38 (1982) 733-739
               2-THETA      INTENSITY    D-SPACING   H   K   L   Multiplicity
                27.31          3.06        3.2660    2   0   0         2
                29.78          6.49        3.0000    0   2   0         2
                29.78         36.72        3.0000   -1   1   1         4
                40.84          4.31        2.2094    1   1   1         4
                40.84         21.44        2.2094    2   2   0         4
                40.84          8.03        2.2094   -3   1   1         4
                42.18          1.13        2.1423    0   2   1         4
                42.18         90.44        2.1423   -2   2   1         4
                44.25         70.76        2.0467    3   1   0         4
                52.86          3.37        1.7321   -1   3   1         4
                52.86          1.69        1.7320   -2   0   2         2
                56.34          3.24        1.6330    4   0   0         2
                57.12         34.22        1.6126   -1   1   2         4
                58.79          1.43        1.5706    2   2   1         4
                58.79          1.94        1.5706   -4   2   1         4
                60.50          8.31        1.5302    1   3   1         4
                60.50         29.18        1.5302    0   0   2         2
                60.50         58.36        1.5302   -3   3   1         4
                60.50          4.15        1.5302   -4   0   2         2
                61.85          3.75        1.5000   -2   2   2         4
                65.03          6.16        1.4343    3   1   1         4
                68.88          3.90        1.3631    2   4   0         4
                68.88          1.42        1.3631    0   2   2         4
                69.83         17.55        1.3469   -2   4   1         4
                71.33          1.16        1.3222    1   1   2         4
                74.30          1.90        1.2765    5   1   0         4
                80.91          1.86        1.1882    3   3   1         4
                80.91         18.82        1.1882    2   0   2         2
                80.91         37.63        1.1882   -5   3   1         4
                85.67          1.31        1.1339   -1   5   1         4
                85.67          1.31        1.1339   -2   4   2         4
                85.85          6.88        1.1320    4   2   1         4
================================================================================
       XPOW Copyright 1993 Bob Downs, Ranjini Swaminathan and Kurt Bartelmehs
  For reference, see Downs et al. (1993) American Mineralogist 78, 1104-1107.