Garg A B, Liang A, Errandonea D, Rodríguez-Hernández P, Muñoz A
High Pressure and Synchrotron Radiation Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India.
Homi Bhabha National Institute, Anushaktinagar, Mumbai 400094, India.
J Phys Condens Matter. 2022 Feb 28;34(17). doi: 10.1088/1361-648X/ac5202.
We have carried out a high-pressure study on monoclinic fergusonite-type YbNbO. Synchrotron powder x-ray diffraction experiments and density-functional theory simulations have been performed. We found a gradual increase of symmetry under compression, with calculations predicting a second-order monoclinic-tetragonal transition at 15 GPa. However, experiments provided evidence of a transition at 11.6 GPa to a triclinic structure, described by space groupP1¯. The appearance of the triclinic phase, which according to calculations is dynamically unstable under hydrostatic conditions, seems to be related to the presence of non-hydrostatic stresses. The triclinic high-pressure phase remains stable up to 31.9 GPa and the phase transition is not reversible. We have determined the pressure dependence of unit-cell parameters of both phases and calculated their room-temperature equation of state. For the fergusonite-phase we have also obtained the isothermal compressibility tensor. In addition to the high-pressure studies, we report ambient-pressure Raman and infrared spectroscopy measurements which have been compared with density-functional theory calculations.
我们对单斜铁铌钇矿型YbNbO进行了高压研究。开展了同步辐射粉末X射线衍射实验和密度泛函理论模拟。我们发现压缩下对称性逐渐增加，计算预测在15 GPa时会发生二级单斜-四方转变。然而，实验证明在11.6 GPa时转变为三斜结构，由空间群P1¯描述。根据计算，三斜相在静水条件下是动态不稳定的，其出现似乎与非静水应力的存在有关。三斜高压相在高达31.9 GPa时保持稳定，且相变是不可逆的。我们确定了两个相的晶胞参数的压力依赖性，并计算了它们的室温状态方程。对于铁铌钇矿相，我们还获得了等温压缩率张量。除了高压研究外，我们还报告了常压拉曼光谱和红外光谱测量结果，并与密度泛函理论计算进行了比较。
