Systematic First Principles Configuration-Interaction Calculations of Linear Optical Absorption Spectra in Silicon Hydrides : Si$_2$H$_{2n}$ ($n = 1-3$)

TL;DR

This study uses advanced first-principles calculations to determine the optical absorption spectra of silicon hydrides, providing new spectral data and insights into conformer identification based on optical fingerprints.

Contribution

First-principles spectra for Si₂H₂ and Si₂H₄ are reported for the first time, and the approach reliably matches experimental data for Si₂H₆, advancing computational methods in silicon hydride spectroscopy.

Findings

First spectra for Si₂H₂ and Si₂H₄ conformers.

Excellent agreement with experimental spectra for Si₂H₆.

Optical fingerprints can identify different conformers.

Abstract

We have performed first principles electron-correlated calculations employing large basis sets to optimize the geometries, and to compute linear optical absorption spectra of various low-lying conformers of silicon hydrides: Si$_{2}$H$_{2n}$, $n=1,2,3$. The geometry optimization for various isomers was carried out at the coupled-cluster singles-doubles-perturbative-triples {[}CCSD(T){]} level of theory, while their excited states and absorption spectra were computed using a large-scale multi-reference singles-doubles configuration-interaction (MRSDCI) approach, which includes electron-correlation effects at a sophisticated level. Our calculated spectra are the first ones for Si$_{2}$H$_{2}$ and Si$_{2}$H$_{4}$ conformers, while for Si$_{2}$H$_{6}$ we obtain excellent agreement with the experimental measurements, suggesting that our computational approach is reliable. Our calculated absorption spectra exhibit a strong structure-property relationship, suggesting the possibility of identifying various conformers based on their optical absorption fingerprints. Furthermore, we have also performed geometry optimization for the selected optically excited states, providing us insights into their character.