PRESSURE-INDUCED ZIRCON TO MONAZITE PHASE TRANSITION IN Y1-хLaхPO4: FIRST-PRINCIPLES CALCULATIONS
I. R. Shein, E. V. Shalaeva
Institute of Solid State Chemistry, Ural Branch, Russian Academy of Sciences, Ekaterinburg, Russia
Keywords: ортофосфаты LaPO-YPOsub>4, ab initio расчеты, барические превращения, фазовая стабильность, LaPO-YPO orthophosphates, ab initio calculations, pressure-induced transformations, phase stability
Abstract
Density functional theory was used to study pressure-induced phase transitions of zircon to monazite in doped yttrium orthophosphate, Y1- х La х PO4, for х = 0, 0.0625, 0.125. The pressures of the phase transition, the elastic moduli and the universal elastic anisotropy index were calculated. It was shown that with increasing lanthanum concentration in Y1- x La x PO4, the transition pressure increases. According to the Birch-Murnaghan equation of state, this effect is associated with a decrease in the critical volume. The increased stability of the doped zircon phase compared to YPO4 is attributed to the more significant increase in the anisotropy and distortions of REO8 polyhedra and RE-O-P chains found for the optimized structures at critical volumes.
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