We have determined the unit-cell parameters of diaspore α -AlO(OH) at high pressures (13.5-27.8 GPa) and at high temperature (1900 K). Experimental data are compared with the theoretically predicted crystal structure variations derived from density functional theory (DFT) calculations. The experimental analysis establishes that the a axial direction is more compressible than the b and c axial directions in the low-pressure range (13.5-18 GPa) and at 1900 K, whereas all three directions show similar behaviors in the high-pressure range (18-27.8 GPa). The diaspore isothermal bulk modulus KT values are 137.6 GPa, 124.8 GPa, and 141.3 GPa, respectively, at 300 K, at 1900 K, and again at 300 K after quenching. By comparison, the diaspore isothermal bulk modulus KT computed at 300 K and at ambient pressure in the framework of the plane-wave pseudopotential approach is equal to 129.3 GPa.
ASJC Scopus subject areas
- Physics and Astronomy (miscellaneous)