Arsenic
Diffraction data computed using the structure from the paper listed below,
along with the cell parameters refined from the powder pattern for R050653
      Wyckoff R W G
      Crystal Structures 1 (1963) 7-83
      Second edition. Interscience Publishers, New York, New York

      CELL PARAMETERS:   4.131582   4.131582   4.131582   54.15052   54.15052   54.15052
      SPACE GROUP: R-3m
      X-RAY WAVELENGTH:     1.541838
               2-THETA      INTENSITY    D-SPACING   H   K   L
                25.36         13.38        3.5149    1   1   1
                28.70          3.42        3.1121    1   0   0
                32.32        100.00        2.7710    1   1   0
                44.20         29.89        2.0491    2   1   1
                48.40         33.32        1.8805    0  -1   1
                51.62         12.72        1.7703    2   2   1
                52.03          3.37        1.7575    2   2   2
                55.40          8.27        1.6581    2   1   0
                59.38         15.72        1.5560    2   0   0
                67.59          7.63        1.3855    2   2   0
                80.00         12.08        1.1988    2  -1   1
                80.00         12.08        1.1988    2  -1   1
       XPOW Copyright 1993 Bob Downs, Ranjini Swaminathan and Kurt Bartelmehs
  For reference, see Downs et al. (1993) American Mineralogist 78, 1104-1107.