The high-pressure behavior of manganese diselenide MnSe2 was investigated by synchrotron angle-dispersive X-ray diffraction (ADXRD) and infrared reflection spectroscopy equipped with a diamond-anvil cell. It was found that MnSe2 with a pyrite-type structure undergoes a transformation into a disordered intermediate phase at ~ 12.5 GPa, with a ground state composed of an arsenopyrite-type structure, as confirmed by laser-heating treatment. The pyrite to arsenopyrite phase transition was found to be coupled to a large collapse in the unit-cell volume (∆V ~ 19%) and an electronic transition from a high-spin to low-spin state for manganese cations (Mn2+). With a fixed value for the pressure derivation of the bulk modulus K' = 4, fitting of the pressure–volume data to a second-order Birch–Murnaghan equation of state yielded isothermal bulk modulus values of K0 = 56.1(9) GPa and K0 = 93.1(4) GPa for the pyrite-type and arsenopyrite-type phases, respectively. The measured infrared reflectivity (Rsd) for MnSe2 showed a drastic increase at pressures between 13 and 20 GPa, but became insensitive to pressure under further compression, implying a pressure-induced transition from an insulator to metallic state.

中文翻译：

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MnSe2 中的压力诱导结构转变和金属化

通过同步加速器角色散 X 射线衍射 (ADXRD) 和配备金刚石砧座的红外反射光谱法研究了二硒化锰 MnSe2 的高压行为。发现具有黄铁矿型结构的 MnSe2 在~12.5 GPa 时会转变为无序的中间相，其基态由毒砂型结构组成，这通过激光加热处理得到证实。发现黄铁矿到毒砂的相变与晶胞体积的大坍塌 (ΔV ~ 19%) 以及锰阳离子 (Mn2+) 从高自旋状态到低自旋状态的电子跃迁相耦合。对于体积模量 K' = 4 的压力推导的固定值，将压力-体积数据拟合到二阶 Birch-Murnaghan 状态方程得出黄铁矿型和毒砂型相的等温体积模量值 K0 = 56.1(9) GPa 和 K0 = 93.1(4) GPa，分别。测得的 MnSe2 的红外反射率 (Rsd) 在 13 到 20 GPa 之间的压力下急剧增加，但在进一步压缩下对压力不敏感，这意味着从绝缘体到金属状态的压力诱导转变。