Bonding in the high spin lithium clusters: Non‐nuclear attractors play a crucial role

• Published in: Journal of computational chemistry Vol. 44; no. 9; pp. 962 - 968
• Main Authors: Karachi, Sara Sadat, Eskandari, Kiamars
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley & Sons, Inc 05.04.2023; Wiley Subscription Services, Inc
• Subjects: Bonding strength; Chemical bonds; Clusters; electron density; Electron spin; Electrons; IQA; Lithium; lithium cluster; non‐nuclear attractor; NPFM; Quantum theory; IQA; electron density; non-nuclear attractor; NPFM; lithium cluster
• ISSN: 0192-8651; 1096-987X
• DOI: 10.1002/jcc.27056

The bonding in lithium high‐spin clusters contradicts the usual chemical bonding concept since there are no electron pairs between the atoms, and they are bound with parallel spin electrons. Quantum theory of atoms in molecules and interacting quantum atom analysis (IQA) were used to investigate the nature of bonding in the high‐spin Linn+1n=2−5 clusters. Our findings demonstrate that the non‐nuclear attractors (NNAs) are an essential component of the high‐spin lithium clusters and play a key role in keeping them stable. Based on IQA energy terms, an electrostatic destabilizing interaction between the lithium atoms works against the cluster formation. On the other hand, the interactions between lithium atoms and NNA basins are stabilizing and outweigh the lithium‐lithium destabilizing effects. In fact, NNAs tend to draw lithium atoms together and stabilize the resulting cluster. The high‐spin clusters of lithium can be regarded as electrostatically driven compounds since the electrostatic components are primarily responsible for the stabilizing interactions between NNAs and Li atoms. The only exception is 3Li2, which lacks NNA and has a non‐repellent lithium–lithium interaction. Indeed, in the 3Li2, the interatomic electrostatic component is negligibly small, and the exchange‐correlation term leads to a weak bonding interaction. According to the interacting quantum atom analysis energy terms, there is an electrostatic repulsive force between lithium atoms that acts against the formation of clusters. In contrast, the attractive interactions between lithium atoms and non‐nuclear attractors basins overwhelm the repulsions between lithium atoms.