Villiaumite
Diffraction data computed using the structure from the paper listed below,
along with the cell parameters refined from the powder pattern for R060916
      Deshpande V T
      Acta Crystallographica 14 (1961) 794-794
      Thermal expansion of sodium fluoride and sodium bromide
      Note: T = 29.6 C, rocksalt structure

      CELL PARAMETERS:   4.634000   4.634000   4.634000   90.00000   90.00000   90.00000
      SPACE GROUP: Fm3m
      X-RAY WAVELENGTH:     1.541838
               2-THETA      INTENSITY    D-SPACING   H   K   L
                33.48          1.89        2.6744    1   1   1
                38.85        100.00        2.3161    2   0   0
                56.12         50.68        1.6378    2   2   0
                70.35         12.86        1.3372    2   2   2
                83.39          4.74        1.1581    4   0   0
                83.39          4.74        1.1581    4   0   0
       XPOW Copyright 1993 Bob Downs, Ranjini Swaminathan and Kurt Bartelmehs
  For reference, see Downs et al. (1993) American Mineralogist 78, 1104-1107.