Structure refinement of BaCl2.D2O and SrCl2.D2O by neutron powder diffraction

Neutron powder diffraction intensities have been measured for BaCl2.D2O at 295 and 1.5 K and SrCl2.D2O at 295 K (Pnma, Z=4, Rwp=10.5%, 9.8%, and 10.2%, respectively). The structure data confirm the results of single crystal X-ray structure determination with respect to the heavy atoms. Additionally, previous spectroscopic findings can now be related to structural features. The previous interpretation of the two hydrogen bonds present in BaCl2.D2O must be changed. Apart from the stronger hydrogen bond of the barium compound, which is nearly single in nature, all H-bonds of the isostructural MCl2.H2O (M=Ba, Sr; X=Cl, Br, I) are bifurcated. Bifurcated H-bonds have been found to be stronger than expected from the individual H .. Cl- distances because of the combined action of the two hydrogen bond acceptors. (orig.)