Structural Analysis of Phosphorus and Arsenic Clusters: A Comparative DFT and MP2 Study

Abstract

Phosphorus and arsenic play pivotal roles in semiconductor and material science due to their versatile applications. We have employed Gaussian 16 software to optimize 20 initial phosphorus (P₄) and arsenic (As₄) cluster geometries, as well as 32 As₂P₂ cluster geometries, utilizing B3LYP and MP2 methods with the 6-311++G(3d2f,3p2d) basis set. The geometries were rigorously validated through frequency calculations, followed by energy calculations using B3LYP/aug-cc-pVQZ and MP2/aug-cc-pVQZ. We thoroughly analyzed and justified the observed disparities between DFT and MP2 results. Notably, a compelling linear relationship was observed in the energy gap between the most stable and the second most stable geometries from P₄ to As₄ in both MP2 and B3LYP calculations, with MP2 results aligning closely with additional CCSD(full) calculations. Additionally, our investigation unveiled two enantiomeric geometries of As₄, specifically the semirectangular shape, with slight energy variations reminiscent of parity violation observed in amino acids. These findings significantly enhance our comprehension of pnictogen cluster stability, offering insights into the semiconductor and material science.