Pyroxene-ideal
      Thompson R M, Downs R T
      American Mineralogist 89 (2004) 614-628
      Model pyroxenes II: Structural variation as a function of tetrahedral rotation
      model with O3-O3-O3 angle = 240 and model oxygen radius = 1
      Note: Atoms Mg, Si, and O are assigned to atomic positions for convenience
      _database_code_amcsd 0003471

      CELL PARAMETERS:    7.3940   6.0000   3.4640   90.000  117.900   90.000
      SPACE GROUP: C2/c      
      X-RAY WAVELENGTH:     1.541838
      Cell Volume:    135.814
      Density (g/cm3):      9.818
      MAX. ABS. INTENSITY / VOLUME**2:      21.71105449    
      RIR:      0.720
      RIR based on corundum from Acta Crystallographica A38 (1982) 733-739
               2-THETA      INTENSITY    D-SPACING   H   K   L   Multiplicity
                20.09          1.00        4.4196    1   1   0         4
                27.30          3.39        3.2673    2   0   0         2
                29.78          7.18        3.0000    0   2   0         2
                29.78         40.61        2.9999   -1   1   1         4
                40.82          4.78        2.2104    1   1   1         4
                40.84         23.73        2.2098    2   2   0         4
                40.85          8.88        2.2092   -3   1   1         4
                42.17          1.25        2.1427    0   2   1         4
                42.19        100.00        2.1421   -2   2   1         4
                44.24         78.35        2.0474    3   1   0         4
                52.86          3.73        1.7320   -1   3   1         4
                52.86          1.87        1.7320   -2   0   2         2
                56.32          3.59        1.6336    4   0   0         2
                57.11         37.86        1.6128   -1   1   2         4
                58.77          1.58        1.5712    2   2   1         4
                58.79          2.15        1.5706   -4   2   1         4
                60.48         32.32        1.5307    0   0   2         2
                60.49          9.19        1.5305    1   3   1         4
                60.51         64.53        1.5301   -3   3   1         4
                60.52          4.59        1.5299   -4   0   2         2
                61.86          4.15        1.5000   -2   2   2         4
                64.99          6.82        1.4350    3   1   1         4
                68.86          1.57        1.3635    0   2   2         4
                68.88          4.32        1.3632    2   4   0         4
                68.89          1.00        1.3629   -4   2   2         4
                69.83         19.41        1.3469   -2   4   1         4
                71.30          1.29        1.3227    1   1   2         4
                74.27          2.11        1.2770    5   1   0         4
                80.86         20.85        1.1888    2   0   2         2
                80.87          2.06        1.1886    3   3   1         4
                80.90         41.63        1.1882   -5   3   1         4
                80.92          1.03        1.1880   -6   0   2         2
                85.67          1.45        1.1339   -1   5   1         4
                85.67          1.45        1.1339   -2   4   2         4
                85.80          7.63        1.1325    4   2   1         4
                88.52          1.32        1.1046   -6  -2   2         4
================================================================================
       XPOW Copyright 1993 Bob Downs, Ranjini Swaminathan and Kurt Bartelmehs
  For reference, see Downs et al. (1993) American Mineralogist 78, 1104-1107.