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 = 120 and model oxygen radius = 1
      Note: Atoms Mg, Si, and O are assigned to atomic positions for convenience
      _database_code_amcsd 0003477

      CELL PARAMETERS:    6.6332   6.0000   3.4640   90.000  100.000   90.000
      SPACE GROUP: C2/c      
      X-RAY WAVELENGTH:     1.541838
      Cell Volume:    135.770
      Density (g/cm3):      9.821
      MAX. ABS. INTENSITY / VOLUME**2:      24.76687886    
      RIR:      0.821
      RIR based on corundum from Acta Crystallographica A38 (1982) 733-739
               2-THETA      INTENSITY    D-SPACING   H   K   L   Multiplicity
                27.30          2.97        3.2662    2   0   0         2
                29.78          6.30        3.0000    0   2   0         2
                31.18          2.47        2.8682   -1   1   1         4
                35.07          4.92        2.5588    1   1   1         4
                40.02         11.29        2.2528    0   2   1         4
                40.84         20.80        2.2094    2   2   0         4
                44.25         68.67        2.0469    3   1   0         4
                46.26         21.89        1.9626   -2   2   1         4
                47.95         19.78        1.8971   -3   1   1         4
                51.88         41.33        1.7624    2   2   1         4
                53.74         33.34        1.7057    0   0   2         2
                53.75         66.66        1.7055   -1   3   1         4
                55.42          4.18        1.6580   -1   1   2         4
                56.04          7.57        1.6410    3   1   1         4
                56.34          3.15        1.6331    4   0   0         2
                56.34          6.29        1.6331    1   3   1         4
                56.35          3.14        1.6327   -2   0   2         2
                60.43          9.04        1.5320    1   1   2         4
                65.24         19.34        1.4302   -3   1   2         4
                66.05          8.55        1.4145    2   0   2         2
                66.07         17.06        1.4141   -3   3   1         4
                66.78          6.41        1.4008   -4   2   1         4
                68.31          2.30        1.3731    0   4   1         4
                68.88          3.79        1.3631    2   4   0         4
                72.83          4.78        1.2987   -2   4   1         4
                74.11          4.74        1.2794    2   2   2         4
                74.30          1.85        1.2766    5   1   0         4
                77.23         11.17        1.2353    2   4   1         4
                78.66          3.71        1.2163    3   1   2         4
                80.68          2.28        1.1909   -4   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.