Effect ofmechanical activation and hydrostatic pressure on the crystal structure of brucite

Ultrafine brucite powder was prepared by the high energy ball-milling method with brucite mineral as raw material. The effect of ball-milling time on the lattice structure and the mean particle size was analyzed by X-ray diffraction(XRD),Fourier-transform infrared spectroscopy (FTIR) and laser particle(LP). The mechanism of different hydrostatic pressures on the crystal structure of brucite was studied by the first principles calculation. The experimental results show that the crystal structure is more easily distorted along the [001] direction with the mechanical activation, and that, with longer ball-milling the peaks of IR spectrum in brucite exhibit blue-shift and broadening, and the ultrafine brucite powder with the mean particle size of 3.56 μm is obtained after ball-milling for 3 h. The theoretical results show that the lattice constant a decreases linearly and c decreases nonlinearly as the hydrostatic pressure increases. The band gap increases with the increases in pressure, which is mainly due to the conduction band of Mg 2p shifts to the high energy direction. The comparison of Mulliken population and electronic density difference of brucite crystal at 0 GPa and 10.9 GPa shows that the O—H bond is a strong covalent bond and the bond length remains unchanged with the increase in hydrostatic pressure. When the hydrostatic pressure increasing to 10.9 GPa, the H disorder decreases with the H…O′ bond rearrangement, which is consistent with the previous experimental results.