[sdpd] C4H4CuAlCl4

[Armel Le Bail <armel... @fluo.univ-lemans.fr>]

Let us continue this crowdy discussion.

Some new results on C4H4CuAlCl4 :

Using the molecule location option in ESPOIR,
with a CuAlCl4 model taken from the CuAlCl4C6H6
structure in CSD, one may obtain Rp(F)=33% in
the P212121 space group previously suggested.

Refining this model with FULLPROF leads to :

 Cu    0.0873  1.0014 -0.0061  
 Al    0.2419  0.8388  0.2950  
 Cl1   0.1090  1.0064  0.2448  
 Cl2   0.2356  0.8555  0.4783  
 Cl3   0.3989  0.9100  0.2402  
 Cl4   0.2207  0.5607  0.2418  

 => Cell parameters      :
                             12.65127   0.00258
                              7.21250   0.00185
                             12.19595   0.00222

 => Conventional Rietveld R-factors ==>
 => Rp: 35.9     Rwp: 29.2     Rexp:   28.59 Chi2:  1.04    
 => Bragg R-factor:  25.9       Vol: 1112.846( 0.418)  
 => Rf-factor= 22.4             

The refinement includes a constraint on Al-Cl distances.

Fourier difference by SHELXL or searching C atoms
 from scratch by ESPOIR then suggest positions
for the remaining atoms. However, they may be ghosts
since interatomic distances are not very satisfying.

The question is (I am not a very good in organic
chemistry :-() what is the C4H4 arrangement : two C2H2
or a single linear C4H4 ???

Best,

Armel