On the Nature of Optical Excitations in Hydrogenated Aluminium Cluster Al4H6: A Theoretical Study

TL;DR

This theoretical study investigates the optical excitations of hydrogenated aluminium cluster Al4H6, revealing that hydrogenation shifts excitations from plasmonic to single-particle nature, with results aligning well with previous ab initio methods.

Contribution

It provides a detailed theoretical analysis of Al4H6's photoabsorption spectrum using semi-empirical methods, highlighting the impact of hydrogenation on excitation characteristics.

Findings

Excitations are dominated by single-particle transitions.

Hydrogenation alters the nature of optical excitations.

Results agree with previous ab initio calculations.

Abstract

In this paper, we present a theoretical investigation of photoabsorption spectrum of the newly synthesized hydrogenated cluster of aluminium, Al4H6. The calculations are performed within the wave-function-based semi-empirical method employing the complete neglect of differential overlap (CNDO) model, employing a large-scale configuration interaction (CI) methodology, and our results are found to be in very good agreement with the earlier ones obtained from the ab initio time-dependent density functional theory (TDDFT). We carefully analyse the many-particle wave functions of various excited states up to 8 eV, and find that they are dominated by single-particle band to band excitations. This is in sharp contrast to bare aluminium clusters, in general, and Al4, in particular, whose optical excitations are plasmonic in nature. We attribute this difference to be a consequence of hydrogenation.