Crystal structure of LiH₂PO₄ studied by single-crystal neutron diffraction

Structure of a LiH₂PO₄ (LDP) single crystal has been studied at room temperature and at 100K by means of neutron diffraction. The LiO₄ tetrahedra in LDP are linked by vertices forming chains along the a-axis, and a three-dimensional network is formed by PO₄ groups connected by two different hydrogen bonds. The Li⁺ ions in this structure were found to be quite immobile in spite of their very light mass; The very high proton conductivity in the system may have directly to do with the relatively weak hydrogen bonds and the relatively long interoxygen distances facilitating reorientation of the proton acceptor complexes, rather than with the Li⁺ ionic motions.