Disorder in gehlenite Ca2Al2SiO7 compound, based on lterature data 

Florian, P., Veron, E., Green, T. F. G., Yates, J. R., & Massiot, D. (2012). 
Elucidation of the Al/Si ordering in gehlenite Ca2Al2SiO7 by combined 
29Si and 27Al NMR spectroscopy/quantum chemical calculations. 
Chemistry of Materials, 24(21), 4068–4079. doi:10.1021/cm3016935

Ca2Al2SiO7.cif - initial structure.
Ca2Al2SiO7_abg.cif - modified structure for large supercell permutations calculations.

Supercell should be installed. See Supporting materials for details.
