DETERMINATION OF THE HYDROGEN POSITION IN CS3H(SEO4)(2) AT 483 K

The structure of the proton conducting phase of Cs3H(SeO4)(2) has been investigated by high resolution neutron powder diffraction at 483 K. A precise localisation of the hydrogen position results in a double-mi nimum-potential in the hydrogen bridge with a H...H distance of 0.77 ( 3) Angstrom. The hydrogen bridge has an O(2)-O(2) distance of 2.66 (2) Angstrom with an expected value of 1.01 (3) Angstrom for the O(2)-H d istance. The angle O(2)-H...O(2) of 163 (3)degrees elucidates the stro ngly non-linear hydrogen bridge.