Institute of Experimental Mineralogy
                 Russian Academy of Sciences
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           142432, Chernogolovka, Moscow district
             A.V. Chichagov  +7(496)52-22320

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VILLIAUMITE

3, t-halite, syn, at 176'C, g-villiaumite

NaF


Cubic  F m3m  Z = 4

Fm3m

8 .10 .12

Ref.Str.:

         Deshpande V.T. (1961)

         * Acta Cryst., 14, 794-794

         R: In the article there are structure data for synthetic villiaumite

         at different temperatures from 29.6'C up to 254'C. N.A.D.

                   Initial data from BDM-file 

   Lattice parameters (cub. angs.,degr.):

             a =   4.6585   alpha =   90.0 
             b =   4.6585   beta  =   90.0 
             c =   4.6585   gamma =   90.0 

    Unit cell volume (cub. angs.) =   101.1 

    Molar volume ( cub.cm/mol.) =    15.22

  Co-ordinates, thermal parameters, occupation for atomic positions:

NoP   x/a     y/b     z/c    B(j)   atom  / occupation

   1 0.0     0.0     0.0      0.0    Na    = 1.00
   2 0.5     0.5     0.5      0.0    F     = 1.00


  Co-ordinates for all atomic positions :

   No       NoP      x/a        y/b       z/c 

     1       1     0.0        0.0        0.0   
     2       2     0.5        0.5        0.5   
     3       1     0.5        0.0        0.5   
     4       1     0.5        0.5        0.0   
     5       1     0.0        0.5        0.5   
     6       2     0.0        0.5        0.0   
     7       2     0.0        0.0        0.5   
     8       2     0.5        0.0        0.0   


X-ray density (g/cm cub.)   =      2.76

MU (1/cm) =      65.914    Mass attenuation coefficient (cm**2/g) =     23.901

 Selected interatomic distances (cation-anion,anion-anion):

 NoP    Atom              Rad.sph.      C.N.    Distance     NoP N.
                           (angs.)               (angs.)

    1    Na                  2.772        6
                                                 2.3293       2
                                                 2.3293       2
                                                 2.3293       2
                                                 2.3293       2
                                                 2.3293       2
                                                 2.3293       2
    2    F                   3.192        0

  X-ray diffraction powder data (II),  X-Ray W.L. =   1.54056(angs.):

  No   H   K   L   Theta 2*Theta    S       LPG   MF        F          I int.
                    ( degree )                                         *100

    1   1   1   1 16.642  33.284   0.186   21.62    8        6.6       73.0
    2   2   0   0 19.311  38.622   0.215   15.6     6       59.2     3208.9
    3   2   2   0 27.884  55.767   0.304    6.81   12       48.2     1855.4
    4   1   1   3 33.257  66.515   0.356    4.61   24        7.4       59.7
    5   2   2   2 34.945  69.89    0.372    4.16    8       40.6      535.9
    6   4   0   0 41.407  82.813   0.429    3.1     6       35.1      223.7


  X-ray diffraction powder data (I)...X-Ray wave length =  1.54056 (angs.):

  No   H   K   L   Theta 2*Theta    d           I int   I int.n.  I p.h.n.   H(Si)
                    ( degree )   (angstrem)     *100                         *100

    1   1   1   1  16.642  33.284  2.68959       73.0      2.3      2.3     5.6
    2   2   0   0  19.311  38.622  2.32925     3208.9    100.0    100.0     5.7
    3   2   2   0  27.884  55.767  1.64703     1855.4     57.8     56.7     5.8
    4   1   1   3  33.257  66.515  1.40459       59.7      1.9      1.8     5.9
    5   2   2   2  34.945  69.89   1.34479      535.9     16.7     16.0     5.9
    6   4   0   0  41.407  82.813  1.16462      223.7      7.0      6.5     6.1

Reference:
Chichagov A.V. et al.
Information-Calculating System on Crystal Structure Data of Minerals
(MINCRYST)
- Kristallographiya, v.35, n.3, 1990, p.610-616 (in Russian)