Santamaría-Pérez David, Chuliá-Jordán Raquel, Otero-de-la-Roza Alberto, Ruiz-Fuertes Javier, Pellicer-Porres Julio, Popescu Catalin
MALTA Consolider Team, Departamento de Física Aplicada-ICMUV, Universitat de València, 46100 Valencia, Spain.
Departamento de Didáctica de las Ciencias Experimentales y Sociales, Universitat de Valencia, 46022 Valencia, Spain.
ACS Omega. 2023 Mar 8;8(11):10403-10410. doi: 10.1021/acsomega.2c08215. eCollection 2023 Mar 21.
We report the structural behavior and compressibility of minrecordite, a naturally occurring Zn-rich dolomite mineral, determined using diamond-anvil cell synchrotron X-ray diffraction. Our data show that this rhombohedral CaZnMg(CO) carbonate exhibits a highly anisotropic behavior, the axis being 3.3 times more compressible than the axis. The axial compressibilities and the equation of state are governed by the compression of the [CaO] and [ZnO] octahedra, which are the cations in larger proportion in each layer. We observe the existence of a dense polymorph above 13.4(3) GPa using Ne as a pressure-transmitting medium, but the onset pressure of the phase transition decreases with the appearance of deviatoric stresses in nonhydrostatic conditions. Our results suggest that the phase transition observed in minrecordite is strain-induced and that the high-pressure polymorph is intimately related to the CaCO-II-type structure. A comparison with other dolomite minerals indicates that the transition pressure decreases when the ratio Zn/Mg in the crystal lattice of pure dolomite is larger than 1. Density functional theory (DFT) calculations predict that a distorted CaCO-II-type structure is energetically more stable than dolomite-type CaZn(CO) above 10 GPa. However, according to our calculations, the most stable structure above this pressure is a dolomite-V-type phase, a polymorph not observed experimentally.
我们报告了菱锌白云石（一种天然存在的富锌白云石矿物）的结构行为和压缩性，其通过金刚石对顶砧同步加速器X射线衍射测定。我们的数据表明，这种菱面体CaZnMg(CO)碳酸盐表现出高度各向异性行为，c轴的可压缩性比a轴高3.3倍。轴向压缩率和状态方程由[CaO]和[ZnO]八面体的压缩控制，它们是每层中比例较大的阳离子。我们使用Ne作为压力传递介质，观察到在13.4(3) GPa以上存在一种致密多晶型物，但在非静水条件下，随着偏应力的出现，相变的起始压力降低。我们的结果表明，在菱锌白云石中观察到的相变是应变诱导的，并且高压多晶型物与CaCO-II型结构密切相关。与其他白云石矿物的比较表明，当纯白云石晶格中的Zn/Mg比大于1时，转变压力会降低。密度泛函理论(DFT)计算预测，在10 GPa以上，扭曲的CaCO-II型结构在能量上比白云石型CaZn(CO)更稳定。然而，根据我们的计算，在此压力以上最稳定的结构是白云石-V型相，这是一种未通过实验观察到的多晶型物。
