The high-pressure and high-temperature behaviors of manganotantalite Mn(Ta,Nb)₂O₆ have been investigated by single-crystal X-ray diffraction and Raman spectroscopy combined with diamond anvil cell technique, as well as first-principle calculations. A pressure-induced reversible phase transition of manganotantalite occurs at 9.5 GPa and room temperature, accompanied by a large volume collapse (∼7.0%) and drastic color change from brownish-yellow to red. The space groups of low-pressure (LP) and high-pressure (HP) phases are the same (Pbcn), but the coordination numbers of Mn increase from six to eight and Ta increase from six to seven, respectively. The band gap becomes narrow from 2.37 to 1.59 eV. We determined the P-T phase diagram of manganotantalite with a positive Clapeyron slope of dP/dT = 0.0073 GPa/K. The P-V data were fitted to a second-order Birch–Murnaghan equation of state with B₀ = 149(4) GPa for the LP phase and B₀ = 188(3) GPa for the HP phase. The isothermal Grüneisen parameters were determined to be 0.23∼2.03 of the LP phase and 0.59∼0.86 of the HP phase for Raman modes. High-pressure behaviors of Mn(Ta,Nb)₂O₆ indicate that this kind of material is a potential effective pressure sensor to monitor pressure change or warn pressure abnormality.

中文翻译：

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Mn（Ta，Nb）₂ O _6中的压力诱导相变：实验研究和第一性原理研究

通过单晶X射线衍射和拉曼光谱结合金刚石砧盒技术，研究了锰金刚玉Mn（Ta，Nb）₂ O ₆的高压和高温行为，以及第一性原理计算。锰锰矿的压力诱导可逆相变发生在9.5 GPa和室温下，伴随着大体积塌陷（〜7.0％），颜色从棕黄色到红色急剧变化。低压（LP）和高压（HP）相的空间群相同（Pbcn），但是Mn的配位数分别从6增加到8和Ta从6增加到7。带隙从2.37缩小至1.59 eV。我们确定了P - T具有正Clapeyron斜率d P / d T = 0.0073 GPa / K的锰锰锌矿的相图。该P - V数据拟状态的二阶桦木-Murnaghan状态方程乙₀ = 149（4）GPA为LP相和乙₀ = 188（3）GPA为HP相。对于拉曼模式，等温Grüneisen参数确定为LP相的0.23-2.03和HP相的0.59-0.86。Mn（Ta，Nb）₂ O ₆的高压行为表明，这种材料是监测压力变化或警告压力异常的潜在有效压力传感器。