Thenardite
Diffraction data computed using the structure from the paper listed below, 
along with the cell parameters refined from the powder pattern of R040183
      Hawthorne F C, Ferguson R B
      The Canadian Mineralogist 13 (1975) 181-187
      Anhydrous sulphates. I: Refinement of the crystal structure of celestite
      with an appendix on the structure of thenardite

      CELL PARAMETERS:   9.8196 12.3047  5.8613   90.000   90.000   90.000
      ALTERNATE SETTING FOR SPACE GROUP: Fddd      

           ATOM        X         Y         Z     OCCUPANCY  ISO(B)
            Na     0.44160   0.12500   0.12500     1.000     1.511
            S      0.12500   0.12500   0.12500     1.000     0.847
            O      0.21380   0.05720   0.97930     1.000     1.431

            X-RAY WAVELENGTH:     1.541838
            BOUNDS ON TWO THETA:    5.0  90.0
            LIMITS IMPOSED ON THE INDICES ARE:  +/-  9 +/- 11 +/-  5
            MAX. ABS. INTENSITY / VOLUME**2:      13.02574232    
            The INTENSITY cut off value is   1.00

               2-THETA      INTENSITY    D-SPACING   H   K   L
                19.05         57.51        4.6583    1   1   1
                23.18         13.41        3.8376    2   2   0
                28.06         42.40        3.1795    1   3   1
                29.03         37.62        3.0762    0   4   0
                32.16        100.00        2.7837    3   1   1
                33.88         44.70        2.6458    0   2   2
                38.39          5.23        2.3448    3   3   1
                38.66         21.11        2.3291    2   2   2
                40.82          3.58        2.2108    1   5   1
                47.38          3.25        1.9188    4   4   0
                48.05          1.72        1.8934    1   1   3
                48.08          1.32        1.8923    2   6   0
                48.84         39.40        1.8648    3   5   1
                49.51          5.58        1.8412    5   1   1
                50.73          5.51        1.7996    4   2   2
                54.62         15.63        1.6802    0   6   2
                55.26          9.55        1.6623    3   1   3
                57.40          5.38        1.6053    4   4   2
                58.02          2.06        1.5897    2   6   2
                58.34          1.80        1.5816    6   2   0
                59.53         13.07        1.5528    3   3   3
                61.31          2.55        1.5119    1   5   3
                61.98          6.27        1.4972    3   7   1
                65.30          6.61        1.4289    6   0   2
                67.58          2.76        1.3862    3   5   3
                68.12          1.17        1.3764    5   1   3
                71.29          4.88        1.3229    0   4   4
                72.52          2.25        1.3034    4   8   0
                73.01          5.86        1.2959    6   4   2
                73.05          1.76        1.2953    1   7   3
                73.10          2.51        1.2945    7   3   1
                74.12          7.19        1.2792    6   6   0
                75.57          1.74        1.2582    4   0   4
                77.38          1.49        1.2333    3   9   1
                78.87          2.64        1.2136    3   7   3
                85.60          2.20        1.1346    7   1   3
                85.61          2.50        1.1345    0  10   2
                89.07          1.07        1.0992    3   1   5
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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.