标题： 预测与合成Mg$_4$Pt$_3$H$_6$：一种在常压下稳定的金属配合物过渡金属氢化物 显示英文标题

标题： Prediction and Synthesis of Mg$_4$Pt$_3$H$_6$: A Metallic Complex Transition Metal Hydride Stabilized at Ambient Pressure

摘要： 具有高临界温度（高$T_c$）的超导氢化物的低压稳定化仍然是一个重大挑战，并且实验验证的超导氢化物通常局限于少数几种结构原型。 三元过渡金属配合物氢化物（氢化物配合物）——通常被视为储氢材料——在低压下表现出大量稳定的化合物，并且最近预测了高$T_c$超导性的可能性。 受这类材料的启发，我们研究了Mg-Pt-H体系中的复杂氢化物形成，该体系中没有已知的三元氢化物化合物。 在理论计算结构预测的指导下，我们成功地利用激光加热金刚石压砧细胞合成了一种新型的复杂过渡金属氢化物， Mg$_4$Pt$_3$H$_6$。 该化合物在8至25 GPa的中等压力下以体心立方结构原型形成。 与大多数已知的氢化物配合物不同，Mg$_4$Pt$_3$H$_6$是金属，其形式电荷被描述为 4[Mg]$^{2+}$.3[PtH$_2$]$^{2-}$。 在减压过程中获得的X射线衍射(XRD)测量结果显示，Mg$_4$Pt$_3$H$_6$在淬火至环境条件后仍保持稳定。磁场和温度相关的电输运测量表明，在环境压力下超导转变温度$T_c$(50%) = 2.9 K，这与理论计算结果合理一致。这些发现阐明了Mg-Pt-H体系中的相行为，并为过渡金属配合物氢化物作为一类富氢超导体提供了宝贵的见解。 显示英文摘要

摘要： The low-pressure stabilization of superconducting hydrides with high critical temperatures ($T_c$s) remains a significant challenge, and experimentally verified superconducting hydrides are generally constrained to a limited number of structural prototypes. Ternary transition-metal complex hydrides (hydrido complexes)-typically regarded as hydrogen storage materials-exhibit a large range of compounds stabilized at low pressure with recent predictions for high-$T_c$ superconductivity. Motivated by this class of materials, we investigated complex hydride formation in the Mg-Pt-H system, which has no known ternary hydride compounds. Guided by ab initio structural predictions, we successfully synthesized a novel complex transition-metal hydride, Mg$_4$Pt$_3$H$_6$, using laser-heated diamond anvil cells. The compound forms in a body-centered cubic structural prototype at moderate pressures between 8-25 GPa. Unlike the majority of known hydrido complexes, Mg$_4$Pt$_3$H$_6$ is metallic, with formal charge described as 4[Mg]$^{2+}$.3[PtH$_2$]$^{2-}$. X-ray diffraction (XRD) measurements obtained during decompression reveal that Mg$_4$Pt$_3$H$_6$ remains stable upon quenching to ambient conditions. Magnetic-field and temperature-dependent electrical transport measurements indicate ambient-pressure superconductivity with $T_c$ (50%) = 2.9 K, in reasonable agreement with theoretical calculations. These findings clarify the phase behavior in the Mg-Pt-H system and provide valuable insights for transition-metal complex hydrides as a new class of hydrogen-rich superconductors.