Han Chenxu, Zong Hongxiang, Ding Xiangdong, Sun Jun, Ackland Graeme J
State Key Laboratory for Mechanical Behavior of Materials, School of Materials Science and Engineering, Xi'an Jiaotong University, Xi'an 710049, Shaanxi, China.
Centre for Science at Extreme Conditions, School of Physics and Astronomy, The University of Edinburgh, Edinburgh EH9 3FD, United Kingdom.
Proc Natl Acad Sci U S A. 2025 Jul;122(26):e2424701122. doi: 10.1073/pnas.2424701122. Epub 2025 Jun 24.
Liquid-liquid phase transitions (LLPTs) are typically characterized as two-state systems, where transitions occur between two distinct liquid phases driven by local structural rearrangements. In this study, we observed a continuous LLPT with an inversion of electronegativity in a K-Rb binary alloy. This uniquely exhibits a three-state system behavior. The transition, induced by pressure-driven reordering of electronic orbital energies, progresses through a sequence from -metal to electride to -metal, accompanied by a valence reversal: Potassium transitions from a negative to a positive valence, while rubidium undergoes the opposite shift. This process is marked by two successive anomalies in the alloy's optical, thermodynamic, and dynamic properties over a broad pressure range. The observation of similar LLPT phenomena in other alkali and alkaline earth metal liquids suggests that this three-state system mechanism may provide broader insights into the nature of continuous phase transitions.
液-液相转变（LLPTs）通常被描述为双态系统，其中转变发生在由局部结构重排驱动的两个不同液相之间。在本研究中，我们在一种K-Rb二元合金中观察到了具有电负性反转的连续LLPT。这独特地呈现出三态系统行为。该转变由压力驱动的电子轨道能量重排引起，从-金属到电子化物再到-金属依次进行，伴随着价态反转：钾从负价转变为正价，而铷则发生相反的变化。在很宽的压力范围内，该合金的光学、热力学和动力学性质出现两个连续异常，标志着这一过程。在其他碱金属和碱土金属液体中观察到类似的LLPT现象，表明这种三态系统机制可能为连续相变的本质提供更广泛的见解。
