Theoretical investigation of bonding in diaspore

The bulk modulus of diaspore, alpha -AlOOH, has been obtained from density functional theory based calculations. The value obtained, B = 148 GPa, is consistent with that previously obtained from elastic constant measurements, but in strong disagreement with values derived from high pressure x-ray diffraction experiments. A Mulliken bond population analysis of the electronic structure implies that the Al-O bonds are significantly covalent, in contrast to findings based on an earlier x-ray diffraction study. On compression, the main change is the increase in the hydrogen-bond strength.