AI 中文总结
本文基于原子探针层析技术（APT）的进展，明确晶态相变材料（PCMs）采用金属价键（MVB）键合机制，非晶态为共价键，利用量子化学键合图谱可指导PCMs的设计与特性趋势解释。
AI 中文摘要
相变材料（PCMs）可在非晶态与晶态之间快速可逆切换，该转变伴随光电特性的显著变化。本文综述了解释这些特性变化的研究进展，重点关注原子探针层析技术（APT）的进展。该技术通过提供两个关键键合参数来对键合进行分类，最重要的是多重事件概率（PME），它与激光辅助场蒸发中每个成功激光脉冲脱除多个离子的可能性相关。晶态PCMs的PME高于55%，而金属或离子共价固体不存在该特征，这证实晶态PCMs采用了被称为金属价键（MVB）的独特键合机制。晶态PCMs采用MVB，而非晶态PCMs则表现为共价固体，具有低得多的PME，因此PCMs在结晶时会改变其键合，这与键合的量子化学计算结果一致。具有高PME的晶态固体位于金属与离子共价固体之间的狭窄电导率范围内，表明电子定域与离域存在竞争。一张量化化学键合的图谱将金属价键固体定位于相邻原子间约共享一个电子且键合非过于离子性的区域，该量子化学键合图谱现用于寻找和解释不同应用领域中与PCMs相关的特性趋势。
英文摘要
Phase Change Materials (PCMs) can be rapidly and reversibly switched between their amorphous and crystalline state; a transition which is accompanied by a pronounced change of optoelectronic properties. Here progress is reviewed to explain these property changes, focusing on advances by atom probe tomography (APT). This technique classifies bonding by providing two crucial bonding descriptors. Most important is the Probability of Multiple Events (PME), which is related to the likelihood that more than one ion is dislodged per successful laser pulse in laser assisted field evaporation. Crystalline PCMs are characterized by a PME above 55%, not found for metals or iono-covalent solids. This confirms that crystalline PCMs employ a unique bonding mechanism coined metavalent bonding (MVB). While crystalline PCMs employ MVB, amorphous PCMs behave as covalent solids characterized by a much lower PME. PCMs thus change their bonding upon crystallization, consistent with quantum-chemical calculations of bonding. Crystalline solids with a high PME lie in a narrow conductivity range between metals and iono-covalent solids, indicative for a competition between electron localization and delocalization. A map quantifying chemical bonding locates metavalent solids in a region where approximately one electron is shared between adjacent atoms and bonding is not too ionic. This quantum chemical bonding map is now used to find and explain property trends relevant for PCMs in various application domains.
