Change in compression in MOOH oxyhydroxide and implication for hydrogen bond symmetrization

Sano, Asami   ; Yagi, Takehiko*; Okada, Taku*; Goto, Hirotada*; Kagi, Hiroyuki*; Nagai, Takaya*; Kikegawa, Takumi*

InOOH-type MOOH with distorted rutile structure is one of the densest polymorph among oxyhydroxide, and has a strong hydrogen bond. Previous X-ray diffraction study on aluminum oxyhydroxide, -AlOOH(D), reported the change in axial compressibility and axial ratio at high pressure. This change has been attributed to the transition from the structure with asymmetric hydrogen bond (spacegroup P2nm) to disordered or symmetric hydrogen bond (Pnnm), that is previously predicted by theoretical and neutron studies. To investigate the detail of the change in compression mechanism in InOOH-type MOOH, we conducted compression experiments on InOOH-type GaOOH (P2nm) and CrOOH (guyanaite; Pnnm). In GaOOH, similar behavior to -AlOOH was obtained: b/c decreases rapidly as pressure increases to 10 GPa, but it increases at the pressure range from about 10 to 30 GPa. On the other hand, b/c of CrOOH simply increases to 31 GPa.