Unindexed Powder Pattern of the Week

UPPW-5
November 14, 2003

Problem :

Very recent unindexed ICDD entry : 52-0231, delta-ZnP2O7.

Bad crystallized material, produced from an amorphous phase
during a thermal treatment.

No way to improve the crystallinity, but the formula appears well
established, so that one can rely on the chemical-formula-unit
equivalent volume Veq (= Vcell/Z) known for the other varieties :
120.6 and 119.1 A**3 for phases alpha and beta, and 136.0 A**3
for gamma-Zn2P2O7.

From the original paper : "Attempts to index these data were
unsuccessful, due to the lack of resolution of the pattern."

But this was in 1998, and many new indexing software were
proposed since 1999...

Can your indexing software propose some probable cell(s) for 
such a bad crystallized compounds ?

Data :

ICDD 52-0231
Delta-ZnP2O7
Wavelength : 1.5406
Ge mono
Reference : T. Bataille, P. Bénard-Rocherullé and D. Louër
J. Solid State Chem. 140 (1998) 62-70.
Standard used : fluorophlogopite 
Comments : zinc phenylphosphonate hydrate was decomposed thermally
under flowing air at 430C. The resulting amorphous phase was
crystallized at 480C.
Measured density : 3.688 g.cm(**-3)
Mwt: 239.92


d(A)   Intensity
4.7223   2
4.5825  61
4.3730   7
4.0441 100
3.7489  47
3.4613  75
3.0451  17
2.8985   7
2.8034  25
2.7345  30
2.6852   8
2.4597  21
2.3836   7
2.3423  28
2.3003  13
2.2339   7
2.1835   2
2.1466   5
2.1080   5
2.0773   3
2.0493   6

If you wish to estimate the peak positions by yourself or if your
software needs for the raw powder pattern, this is possible this
time, thanks to Thierry Bataille who provided the data (the zipped
file contains a .dat for Fullprof (instrm=0) and .raw and .uxd 
Bruker files (use the usual converting software if you need for
other formats).

Plot of a part of the pattern :




RESULTS : less consensus that time...


Most probable cell(s) according to the Participants :

Program            a          b           c        alpha      beta     gamma       V     
                                            M(20)       F 20         Unindexed    Spacegroup

TREOR (SG)       9.201     12.347       4.747       90.       95.47      90.       536.5   
                                           M(19)=11     F19 = 15 (0.0178), 76)         

INDEX (JB)       5.467(2)   5.960(2)    9.436(3)    92.54(1) 100.43(1)  113.32(1)  275.4   
                    (Output of the Le Bail fit using BGMN - one solution among other ones)

TOPAS (AC)      
An unambiguous solution not found
Here are the best results from multiple Pawley refinements using TOPAS
Rwp      SG      Vol       FOM      Zero        a         b          c         al         be        ga
11.33    P-1    327.033    7.49    -0.0323    5.8456    6.2774    9.6566    74.2835    95.8695    76.8442
11.22    P-1    442.470    5.75    -0.0612    6.1076    8.3582    9.8324    68.9356    92.2849   108.5530
10.37    P-1    376.571    5.94     0.0647    4.3101    5.1214    18.6397   81.7647    90.8533    68.0250
10.69    P-1    471.095    5.55     0.0641    5.6743    6.5581    14.2645  100.1809   108.8679    70.1429
10.90    P-1    439.175    6.66     0.0059    7.0758    6.7803    9.4068    94.3569    77.6826    93.4952
11.32    P-1    364.975    7.05     0.0325    4.1818    4.7523    18.6135   99.1342    88.1007    89.4200
11.59    P-1    308.973    8.12    -0.0423    4.7530    7.1309    9.2005    92.9839    95.4271    94.3837
12.00    P-1    258.870    6.67    -0.0501    4.7838    5.9783    9.1892    89.6520    95.5483    81.8427
12.35    P-1    188.300    6.74     0.0654    4.3059    4.9019    9.2427    84.6397    89.7293   104.1062

AUTOX (VZ)       Several probable cells (see the link) :

      A =     3.7675  +-  0.0028
      B =     4.7690  +-  0.0039
      C =     9.2068  +-  0.0048
      alpha =      95.48  +-    0.08
      beta  =      90.10  +-    0.12
      gamma =      84.42  +-    0.13      V = 164.0

      A =     9.2047  +-  0.0053
      B =     6.1447  +-  0.0112
      C =     4.7504  +-  0.0032
      alpha =      90.00  +-    0.00
      beta  =      95.54  +-    0.06
      gamma =      90.00  +-    0.00      V = 267.4

      A =     7.5880  +-  0.0115
      B =     6.0832  +-  0.0088
      C =     9.2882  +-  0.0096
      alpha =      90.00  +-    0.00
      beta  =      99.05  +-    0.12
      gamma =      90.00  +-    0.00     V = 423.4

      A =     9.2003  +-  0.0000
      B =     6.1570  +-  0.0000
      C =     9.4841  +-  0.0000
      alpha =      90.00  +-    0.00
      beta  =      95.61  +-    0.00
      gamma =      90.00  +-    0.00     V = 534.7


McMaille (ALB)   Several probable cells, selected according to the probable Vcell/Z 
             (V~540A**3 for Z=4 or V~270 for Z=2 - not all lines indexed...)
    Rp     Vol        Ind Nsol    a        b         c      alpha  beta  gamma
    Monoclinic cells
   0.089    535.878    19   3   9.2078   6.1581   9.4951  90.000  95.539  90.000
   0.102    534.237    19   2   9.9408   6.1422   9.4904  90.000 112.787  90.000
   0.124    540.327    18   4   8.7493   6.9224   8.9295  90.000  92.461  90.000
    Triclinic cells
   0.130    273.870    19   3   6.9460   6.7715   5.8902  97.303  86.607  93.663


Results from Simona Galli (TREOR), Alan Coelho (TOPAS), Joerg Bergmann (Eflech/Index),
Victor Zlokazov (AUTOX) and Armel Le Bail (McMaille).
        

 
====================================================================================================
    
Plot by WinPlotr of the Le Bail fit with Fullprof by using the monoclinic cell at the
head of the list above from McMaille :

 => Cell parameters      :
                              9.20027   0.00117
                              6.15705   0.00077
                              9.48415   0.00116
                             90.00000   0.00000
                             95.61447   0.00603
                             90.00000   0.00000

 => R-factors (not corrected for background) for Pattern:  1
 => Rp: 10.8     Rwp: 14.6     Rexp:    9.93 Chi2:  2.15      L.S. refinement
 => Conventional Rietveld R-factors for Pattern:  1
 => Rp: 17.0     Rwp: 21.3     Rexp:   14.48 Chi2:  2.15    



The unindexed peak is clearclose to 37°(2-theta)
There is some anisotropic peak broadening not taken into account (isotropic fit).

Could be the solution ???