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

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          ***      W W W - X R A Y P O L       ***
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TRIDYMITE

1, f-silica

SiO(2)


Hexagonal  P 6(3)/mmc  Z = 4

P6(3)/mmc

1 .4 .1988

Ref.Str.:

         Sato M. (1963)

         * Mineral. J. (Japan), 4, 115-130

                   Initial data from BDM-file 

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

             a =   5.03     alpha =   90.0 
             b =   5.03     beta  =   90.0 
             c =   8.22     gamma =  120.0 

    Unit cell volume (cub. angs.) =   180.11

    Molar volume ( cub.cm/mol.) =    27.12

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

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

   1 0.3333  0.6667  0.4375   0.0    Si    = 1.00
   2 0.3333  0.6667  0.25     0.0    O     = 1.00
   3 0.5     0.0     0.0      0.0    O     = 1.00


  Co-ordinates for all atomic positions :

   No       NoP      x/a        y/b       z/c 

     1       1     0.3333     0.6667     0.4375
     2       2     0.3333     0.6667     0.25  
     3       3     0.5        0.0        0.0   
     4       3     0.0        0.5        0.0   
     5       3     0.5        0.5        0.0   
     6       1     0.6667     0.3333     0.9375
     7       2     0.6667     0.3333     0.75  
     8       3     0.5        0.0        0.5   
     9       3     0.0        0.5        0.5   
    10       3     0.5        0.5        0.5   
    11       1     0.3333     0.6667     0.0625
    12       1     0.6667     0.3333     0.5625


X-ray density (g/cm cub.)   =      2.22

MU (1/cm) =      76.313    Mass attenuation coefficient (cm**2/g) =     34.452

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

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

    1    Si                  2.1          4
                                                 1.5412       2
                                                 1.5402       3
                                                 1.5402       3
                                                 1.5402       3
    2    O                   3.264        6
                                                 2.5162       3
                                                 2.5162       3
                                                 2.5163       3
                                                 2.5162       3
                                                 2.5162       3
                                                 2.5162       3
    3    O                   3.264        6
                                                 2.5162       2
                                                 2.515        3
                                                 2.515        3
                                                 2.515        3
                                                 2.515        3
                                                 2.5162       2

  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   0   0 10.185  20.37    0.115   61.05    6       45.2     2305.6
    2   0   0   2 10.802  21.604   0.122   54.04    2       61.2     1248.8
    3   1   0   1 11.544  23.088   0.13    47.05   12       27.2     1285.4
    4   1   0   2 14.932  29.863   0.167   27.31   12       21.2      455.8
    5   1   1   0 17.835  35.67    0.199   18.59    6       39.8      545.5
    6   1   0   3 19.397  38.794   0.216   15.45   12       21.5      265.0
    7   2   0   0 20.711  41.422   0.23    13.35    6        7.1       12.3
    8   1   1   2 21.043  42.086   0.233   12.89   12        6.0       17.2
    9   2   0   1 21.46   42.921   0.237   12.33   12       21.1      202.9
   10   0   0   4 22.014  44.028   0.243   11.65    2       39.7      113.2
   11   2   0   2 23.594  47.187   0.26     9.96   12       20.2      151.0
   12   1   0   4 24.485  48.969   0.269    9.15   12       13.7       63.7
   13   2   0   3 26.858  53.716   0.293    7.42   12       20.1      110.9
   14   2   1   0 27.894  55.789   0.304    6.8    12       29.2      214.3
   15   2   1   1 28.498  56.997   0.31     6.48   24       18.1      156.5
   16   1   1   4 28.95   57.9     0.314    6.25   12        0.0        0.0
   17   1   0   5 30.053  60.106   0.325    5.75   12       32.9      230.6
   18   2   1   2 30.264  60.528   0.327    5.66   24       15.4       99.2
   19   2   0   4 31.02   62.04    0.335    5.36   12       18.6       68.4
   20   3   0   0 32.038  64.076   0.344    4.99    6       32.1       95.0
   21   3   0   1 32.595  65.19    0.35     4.81   12        0.0        0.0
   22   2   1   3 33.08   66.16    0.354    4.66   24       19.3      128.2
   23   0   0   6 34.211  68.423   0.365    4.34    2        8.6        2.0
   24   3   0   2 34.237  68.474   0.365    4.34   12        8.6       11.7
   25   2   0   5 35.946  71.893   0.381    3.93   12       30.1      131.6
   26   1   0   6 36.114  72.229   0.383    3.9    12        7.6        8.3
   27   2   1   4 36.833  73.665   0.389    3.75   24        9.5       24.8
   28   3   0   3 36.896  73.793   0.39     3.74   12        0.0        0.0
   29   2   2   0 37.774  75.548   0.398    3.58    6       54.6      197.5
   30   3   1   0 39.61   79.22    0.414    3.31   12       23.5       67.5
   31   1   1   6 39.811  79.622   0.416    3.28   12       32.4      127.4
   32   2   2   2 39.835  79.67    0.416    3.28   12       32.4      127.2
   33   3   1   1 40.122  80.243   0.418    3.24   24       14.7       51.8
   34   3   0   4 40.507  81.015   0.422    3.19   12        0.0        0.0
   35   2   1   5 41.462  82.924   0.43     3.09   24       27.9      177.5
   36   2   0   6 41.623  83.246   0.431    3.07   12       29.8      101.1
   37   3   1   2 41.647  83.294   0.431    3.07   24       12.9       38.1
   38   1   0   7 42.795  85.589   0.441    2.97   12        4.6        2.4
   39   3   1   3 44.17   88.34    0.452    2.87   24       17.7       66.4


  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   0   0  10.185  20.37   4.35611     2305.6    100.0    100.0     5.6
    2   0   0   2  10.802  21.604  4.11        1248.8     54.2     54.1     5.6
    3   1   0   1  11.544  23.088  3.84903     1285.4     55.8     55.6     5.6
    4   1   0   2  14.932  29.863  2.98943      455.8     19.8     19.6     5.6
    5   1   1   0  17.835  35.67   2.515        545.5     23.7     23.4     5.7
    6   1   0   3  19.397  38.794  2.31933      265.0     11.5     11.3     5.7
    7   2   0   1  21.46   42.921  2.1054       202.9      8.8      8.6     5.7
    8   0   0   4  22.014  44.028  2.055        113.2      4.9      4.8     5.7
    9   2   0   2  23.594  47.187  1.92452      151.0      6.6      6.4     5.7
   10   1   0   4  24.485  48.969  1.85857       63.7      2.8      2.7     5.7
   11   2   0   3  26.858  53.716  1.705        110.9      4.8      4.7     5.8
   12   2   1   0  27.894  55.789  1.64645      214.3      9.3      9.0     5.8
   13   2   1   1  28.498  56.997  1.61439      156.5      6.8      6.5     5.8
   14   1   0   5  30.053  60.106  1.53811      230.6     10.0      9.6     5.8
   15   2   1   2  30.264  60.528  1.52838       99.2      4.3      4.1     5.8
   16   2   0   4  31.02   62.04   1.49471       68.4      3.0      2.8     5.8
   17   3   0   0  32.038  64.076  1.45204       95.0      4.1      3.9     5.9
   18   2   1   3  33.08   66.16   1.41126      128.2      5.6      5.3     5.9
   19   2   0   5  35.946  71.893  1.31217      131.6      5.7      5.4     5.9
   20   2   1   4  36.833  73.665  1.28492       24.8      1.1      1.0     6.0
   21   2   2   0  37.774  75.548  1.2575       197.5      8.6      8.0     6.0
   22   3   1   0  39.61   79.22   1.20817       67.5      2.9      2.7     6.0
   23   1   1   6  39.811  79.622  1.20308      254.7     11.0     10.2     6.0
   24   3   1   1  40.122  80.243  1.19532       51.8      2.2      2.1     6.0
   25   2   1   5  41.462  82.924  1.16335      177.5      7.7      7.1     6.1
   26   2   0   6  41.623  83.246  1.15967      139.2      6.0      5.5     6.1
   27   3   1   3  44.17   88.34   1.10547       66.4      2.9      2.6     6.2

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)