First Principles Study of Structural and Optical Properties of B$_{12}$ Isomers

TL;DR

This study uses advanced quantum chemistry methods to analyze the structures and optical properties of B12 cluster isomers, identifying stable forms and their spectral signatures for potential optical detection.

Contribution

It provides a comprehensive computational analysis of B12 isomers, including geometry, stability, and optical spectra, with detailed vibrational and electronic insights, which were previously unexplored.

Findings

Eleven distinct B12 isomers identified with stability analysis.

Optical absorption spectra linked to specific isomer geometries.

The perfect icosahedral B12 structure is unstable in isolation.

Abstract

In this work we undertake a comprehensive numerical study of the ground state structures and optical absorption spectra of isomers of B$_{12}$ cluster. Geometry optimization was performed at the coupled-cluster-singles-doubles (CCSD) level of theory, employing cc-pVDZ extended basis sets. Once the geometry of a given isomer was optimized, its ground state energy was calculated more accurately at the coupled-cluster-singles-doubles along with perturbative treatment of triples (CCSD(T)) level of theory, employing larger cc-pVTZ basis sets. Thus, our computed values of binding energies of various isomers are expected to be quite accurate. Our geometry optimization reveals eleven distinct isomers, along with their point group, and electronic ground state symmetries. We also performed vibrational frequency analysis on the three lowest energy isomers, and found them to be stable. Therefore, we computed the linear optical absorption spectra of these isomers of B$_{12}$, employing large-scale multi-reference singles-doubles configuration-interaction (MRSDCI) approach, and found a strong structure-property relationship. This implies that the spectral fingerprints of the geometries can be utilized for optical detection, and characterization, of various isomers of B$_{12}$. We also explored the stability of the isomer with with the structure of a perfect icosahedron, with $I_{h}$ symmetry. In bulk boron icosahedron is the basic structural unit, but, our vibrational frequency analysis reveals that it is unstable in the isolated form. We speculate that this instability could be due to Jahn-Teller distortion because five-fold degenerate HOMO orbitals in $I_{h}$ structure are unfilled.