Single-crystal X-ray diffraction results are presented for six hexaammineruthenium (III) salts, viz. [ Ru (NH3)6]2(SO4)35H2O, [ Ru (NH3)6] CdCl5, [ Ru (NH3)6]ZnCl5, [ Ru (NH3)6]Cl2SCN, [ Ru (NH3)6]2(S2O6)3.H2O, and a salt of approximate formula [ Ru (NH3)6]2 [POF5]3.4H2O. The 11 independent cations in these and other published structures do not adopt a single conformation in respect of hydrogen atom disposition. Analysis of the N- Ru -N-H dihedral angles and their correlations strongly suggests that the conformation is random, given the crystallographic site symmetry. The structure with torsional energy calculated at a minimum by ab initio methods is not observed. This suggests that there are only a limited number of interionic geometries feasible in crystallization. Such a limitation suggests that computing crystal structures, with no assumptions as to space group or any other assumption, is not an open-ended problem with excessive alternatives.
Thermal expansion of Pd-based metallic glasses by ab initio methods and high energy X-ray diffraction