Photo-absorption spectra of small hydrogenated silicon clusters using the time-dependent density functional theory

TL;DR

This paper uses time-dependent density functional theory to systematically analyze how hydrogenation affects the photo-absorption spectra of small silicon clusters, revealing size and hydrogenation-dependent spectral behaviors.

Contribution

It provides a comprehensive TDDFT-based analysis of silicon hydride clusters, highlighting the effects of hydrogenation on optical properties and spectral features.

Findings

Small clusters exhibit atomic-like spectra.

Larger clusters show bulk-like spectral behavior.

Hydrogenation alters the optical gap depending on the degree of hydrogenation.

Abstract

We present a systematic study of the photo-absorption spectra of various Si$_{n}$H$_{m}$ clusters (n=1-10, m=1-14) using the time-dependent density functional theory (TDDFT). The method uses a real-time, real-space implementation of TDDFT involving full propagation of the time dependent Kohn-Sham equations. Our results for SiH$_{4}$ and Si$_{2}$H$_{6}$ show good agreement with the earlier calculations and experimental data. We find that for small clusters (n<7) the photo-absorption spectrum is atomic-like while for the larger clusters it shows bulk-like behaviour. We study the photo-absorption spectra of silicon clusters as a function of hydrogenation. For single hydrogenation, we find that in general, the absorption optical gap decreases and as the number of silicon atoms increase the effect of a single hydrogen atom on the optical gap diminishes. For further hydrogenation the optical gap increases and for the fully hydrogenated clusters the optical gap is larger compared to corresponding pure silicon clusters.