On the structural evolution, magnetic modulation, and spectroscopic characteristics of cobalt phosphide clusters: a DFT investigation

Abstract

Tailoring the magnetic properties and spectroscopic characteristics of transition metal (TM) clusters by doping non-metallic atoms is essential for the development of novel superatoms. Here, we employ density functional theory (DFT) to investigate the geometry, stability, electronic structure, and magnetic properties of the Co₄P_n (n = 1–10) clusters. Our findings reveal that, except for Co₄P, the clusters adopt a structure where phosphorus (P) atoms are added to the triangular faces of a Co₄ core. These clusters exhibit high magnetic moments, primarily arising from the d-orbitals of Co atoms. Notably, Co₄P₄ adopts a highly symmetric T_d point group structure, characterized by a core–shell configuration composed of Co₄ and P₄ tetrahedra. This structure, which represents the smallest cluster-based architecture, is confirmed through distance, charge, and orbital analyses, and is thermodynamically stable. Molecular orbital analysis uncovers a well-defined superatomic orbital arrangement of 1S²|1P⁶|2S²|1D¹⁰|2P⁶|1F¹⁴|3S²|2D⁸ with two electrons in parallel spin arrangements in the D orbitals, providing insights into the magnetic behavior of these superatoms. Furthermore, the infrared and Raman spectra of Co₄P₄ are further analyzed to establish a theoretical foundation for interpreting its electronic and geometrical properties. This study offers new perspectives on designing magnetic superatoms and tailoring their spectral response functions for targeted applications.