白钨矿结构钨酸盐高温高压相变及其差应力效应研究

Studies of high-pressure and high-temperature phase transition in scheelite-structured tungstates are helpful for understanding the high-pressure crystal structure of ABO4-type compounds in the deep earth, and the phase transitions of minerals in the transition zone, therefore, that is of great importance in geology and geochemistry. Based on the findings of the metastable phases and the stress effect of the phase transitions, we will carry out that the high-pressure and high-temperatue syntheses using scheelite-structured BaWO4 and PbWO4 as starting materials, and perform the Raman and X-ray diffraction experiments on the scheelite-structured BaWO4 and PbWO4 and its metastable polymorphisms under hydrostatic and non-hydrostatic conditions. At last, the pressure-induced phase transiton sequence of the scheelite-structured BaWO4 and PbWO4, and the mechanism of stress effect in crystals are obtained by our experiments and first-principles density-functional calculations.

白钨矿结构钨酸盐高温高压相变研究，对探索地球深部ABO4型化合物的存在形式、不连续面的结构转变有着重要的地质和地球化学意义。基于对白钨矿结构BaWO4 和PbWO4亚稳晶态的发现和差应力效应对相变的重大影响，我们拟对白钨矿结构BaWO4和PbWO4开展高温高压合成，对各种晶体形态开展准静水压与非静水压常温高压拉曼和衍射实验。分析BaWO4 和PbWO4各晶体结构稳定存在的温度压力范围，差应力对晶体结构的影响机理,结合基于密度泛涵第一性原理计算，绘制白钨矿结构BaWO4和PbWO4的压致相变序列，查明差应力对矿物结构相变的影响机理。

白钨矿结构钨酸盐高温高压相变及其差应力效应研究，从相变应力的剪切失稳机制认识了白钨矿结构钨酸盐在差应力条件下的相变多样性，从热力学的稳定性认识了高温高压实验的亚稳态新结构。白钨矿结构化合物的高压相变和晶体化学行为研究，为探索地球深部高温高压条件下包含稀土和稀有元素的ABO4 型化合物的存在形式及其稳定性研究提供了有效方法，是对以橄榄石、辉石和石榴子石等主矿物在若干不连续面结构转变研究的重要补充，丰富了人们对地球深部物质的认识，有着重要的地球科学意义。