常压下碱金属被认为是自然界中最简单的金属，然而，它们在压力作用下却呈现出复杂的结构相变和新奇的物理化学性质，如形成非公度结构，出现超导电性，甚至发生违反常规认识的金属-绝缘体转变，等等。二元碱金属合金在高压下可以通过改变化学配比产生更加丰富的新相，是高压物理领域发现新现象和探索新规律的重要模型体系，它在高压作用下能否具有碱金属单质的奇特行为，甚至出现新的高压现象，一直是学术界关注的焦点问题。因此，本项目拟基于我国自主发展的CALYPSO结构预测方法，结合基于密度泛函理论的第一性原理计算，构筑二元碱金属合金（如钠-钾、锂-钾和锂-铷体系等）的高压组分相图，系统研究二元碱金属合金高压相结构和物性，揭示化学配比、原子半径和电子壳层数目的变化对二元碱金属合金高压行为的影响，进而获得“组分-结构-性质”的规律性认知，为全面深入的理解碱金属体系的高压行为提供重要的理论储备。

Alkali metals are considered to be simple metals at ambient condition. However, they exhibit a series of complex structural phase transitions with intriguing physical and chemical properties under high pressures, such as the formation of incommensurate structures, appearance of superconductivity and occurrence of the counterintuitive metal-to-insulator transition. Binary alloys of alkali metals can generate even more abundant new phases under compression, which are prototype systems for high-pressure physics to discover new phenomena and new rules. Whether they possess similar properties as those of elemental alkali metals or can generate even more new high-pressure phenomena is a key issue in academia. By means of the CALYPSO structure prediction method and first-principles calculations, the project is trying to construct the high-pressure compositional phase diagrams for binary alloys between alkali metals (Na-K, Li-K and Li-Rb, etc), and systematically investigate their structures and properties. In the meantime, we try to understand the influences of chemical composition, atomic radii, and number of electronic shells on the high-pressure behaviors of these binary alloys, aiming at obtaining the systematic knowledge about the “composition-structure-property” relation, as well as providing knowledge backup for deep understanding the behaviors of alkali metals at high pressure.