The electron distribution of the hydroxide ion in lithium hydroxide

Analysis of recently published X-ray and neutron diffraction data for LiOH reveals that there are pronounced non-spherical deformations of the electrondensity about the oxygen pseudo-atom. Comparison with a theoretical calculation of the electron density for the isolated hydroxide ion shows that these deformations are due to π-like bonding of the oxygen to the neighbouring hydrogen pseudo-atom. The observed features have shapes consistent with the non-spherical electron distribution of an isolated hydroxide ion undergoing rigid-body libration and translation. It is shown that an important effect of the rigid-body libration is a reversal in sign of the effective quadrupole component of the oxygen pseudo-atom electron density.