高压下贵金属锂合金的结构和性质研究

Noble metal (such as Pt, Au, Ir, Ag, etc. ) have strong chemical inertness and higher electronegativity, and being widely used in metallurgy, electronic devices, coating, catalytic and medical pharmaceuticals, etc. Under normal conditions, Noble metal tends to be more easily to lose electrons in the noble metal compounds, showing the cat-ionic positive valence state. While the examples that noble metal acquire electrons and showing negative valence state are rare. The project aims to introduce the extreme high pressure conditions to shorten the atomic spacing and induce electron orbital hybridization, exploring abnormal negative valence state of noble metal. Using swarm-intelligence CALYPSO structure searching simulations method in conjunction with first principles density functional calculations, we aim to carry out systematically and thoroughly theoretical simulations on atomic structures of high pressure phases of different stoichiometric noble metal lithium alloys (such as Pt-Li, Ir-Li, Ag-Li and Os-Li alloys, etc.). By analyzing the energy, electronic properties and chemical bonding characteristics of high pressure phase alloys, we may obtain energetic stable alloy compounds with abnormal negative valance state in noble metal elements, and finally realize the effective regulation on abnormal negative valence state of noble metal elements, which will provide an important theoretical supporting for high pressure experimental synthesis of novel noble metal compounds.

贵金属（如Pt, Au, Ir, Ag等）具有较强的化学惰性和较高的电负性，被广泛应用于冶金、电子器件、镀膜、催化和医疗制药等领域。在常规条件下，贵金属化合物中的贵金属元素易于失去电子，呈现阳离子的正价态，而贵金属元素得到电子，呈现阴离子的负价态例子并不多见。本项目拟引入高压这一极端条件，利用高压手段缩短原子间距，诱导电子轨道杂化，探索贵金属元素的反常负价态。采用基于群体智能的CALYPSO晶体结构预测方法并结合第一性原理计算，对不同化学组分的贵金属锂合金（如Pt-Li, Ir-Li, Ag-Li和Os-Li等合金）的高压相原子结构进行深入、系统的理论模拟，通过分析高压相合金的能量、电子性质、化学成键方式等，获得贵金属元素呈反常负价态的能量稳定合金化合物，最终实现对贵金属元素反常负价态的有效调控，为新型贵金属化合物的高压实验合成提供重要的理论支撑。

总所周知，压力是至关重要的热力学和动力学的变量。由于压力可以很大程度的缩减原子间距，并且修正电子轨道和化学成键，稳定住常温常压下无法合成的特殊材料，因此它是研究材料的物理和化学性质的有效工具。银（Ag）具有最高电导率，最高热导率和最低的阻抗率，因此，银元素在众多的金属元素中是与众不同的。在高压下，我们系统的Li-Ag体系的稳定配比和所对应的结构。Li4Ag成为了新型稳定的化合物。并且也发现了几个其它压制稳定结构。电子态密度和电荷局域函数图谱揭示了所预测结构的金属特性。此研究突出了压力在稳定Li-Ag的反常化学计量比化合物的决定作用。