Helium
      Wyckoff R W G
      Crystal Structures 1 (1963) 7-83
      Second edition. Interscience Publishers, New York, New York
      Sample at T = 2 K
      Hexagonal closest packed, hcp, structure
      _database_code_amcsd 0011177

      CELL PARAMETERS:    3.5700   3.5700   5.8300   90.000   90.000  120.000
      SPACE GROUP: P6_3/mmc  
      X-RAY WAVELENGTH:     1.541838
      Cell Volume:     64.348
      Density (g/cm3):      0.207
      MAX. ABS. INTENSITY / VOLUME**2:     0.4253510670    
      RIR:      0.671
      RIR based on corundum from Acta Crystallographica A38 (1982) 733-739
               2-THETA      INTENSITY    D-SPACING   H   K   L   Multiplicity
                28.88         24.80        3.0917    1   0   0         6
                30.67         27.49        2.9150    0   0   2         2
                32.79        100.00        2.7314    1   0   1        12
                42.63         13.14        2.1209    1   0   2        12
                51.17         12.43        1.7850    1   1   0         6
                55.88         12.60        1.6453    1   0   3        12
                59.83          1.53        1.5459    2   0   0         6
                60.85         11.30        1.5223    1   1   2        12
                62.12          7.69        1.4942    2   0   1        12
                63.87          1.50        1.4575    0   0   4         2
                68.73          1.57        1.3657    2   0   2        12
                71.57          1.29        1.3183    1   0   4        12
                79.17          2.38        1.2098    2   0   3        12
                84.57          1.17        1.1458    2   1   1        24
                86.13          2.15        1.1290    1   1   4        12
                89.92          1.34        1.0910    1   0   5        12
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       XPOW Copyright 1993 Bob Downs, Ranjini Swaminathan and Kurt Bartelmehs
  For reference, see Downs et al. (1993) American Mineralogist 78, 1104-1107.