Photoelectron Spectroscopy and Density Functional Investigation of the Structural Evolution, Electronic, and Magnetic Properties of CrSin– (n = 14–18) Clusters

CrSin– (n = 14–18) cluster anions have been investigated by a combination of photoelectron spectroscopy (PES) and first-principles calculations. The lowest-lying structures of the clusters have been determined by a global minimum search based on the genetic algorithm, combined with density functional theory (DFT) calculations. The simulated PES spectra of the lowest-energy isomers are in agreement with the experimental results, which gives strong evidence that the correct structures have been found. While sizes n = 14 and n = 15 prefer cage-like structures based on multi-center bonding within the cage, the larger sizes adopt structures based on fullerene-type cages around the Cr atom, with the additional atoms attached to the cage surface. A Hirshfeld analysis shows that the Cr atoms act as electron donors in all clusters, thus enhancing the electron count in the cage. It also reveals that the magnetic moment of 1μB shown by all clusters is mainly contributed by the Cr atom. One interesting exception is size 17, where the Cr atom contributes a small moment antiparallel to that of the silicon cage.本研究结合光电子能谱（photoelectron spectroscopy, PES）与第一性原理计算，对CrSin–（n=14~18）团簇阴离子展开了系统性探究。研究人员通过基于遗传算法的全局极小值搜索结合密度泛函理论（density functional theory, DFT）计算，确定了该系列团簇的最低能量稳定结构。最低能量异构体的模拟PES谱与实验结果高度吻合，这为所确定结构的正确性提供了强有力的佐证。其中n=14和n=15的团簇更倾向于采用基于笼内多中心键合的笼状结构；而尺寸更大的团簇则采用以Cr原子为中心的富勒烯型笼状结构，额外的硅原子附着于笼体表面。赫希菲尔德分析（Hirshfeld analysis）显示，所有团簇中的Cr原子均作为电子给体，从而提升了笼结构的电子数。该分析同时揭示，所有团簇展现出的1μB磁矩主要由Cr原子贡献。一个有趣的例外是n=17的团簇，此时Cr原子的磁矩与硅笼的磁矩呈反平行分布。