First-principles structure search for the stable isomers of stoichiometric WS2 nano-clusters

TL;DR

This study uses evolutionary algorithms and density functional theory to identify stable WS2 nano-cluster structures, analyze their electronic and vibrational properties, and determine their stability at various temperatures.

Contribution

It provides a comprehensive first-principles search for stable WS2 nano-cluster isomers across different sizes and temperature conditions, including their electronic and optical properties.

Findings

n=3, 5, 8 are potential low-temperature magic sizes

n=5 and 7 are more stable above 600K

Electronic and vibrational spectra of lowest energy isomers are characterized

Abstract

In this paper, we employ evolutionary algorithm along with the full-potential density functional theory (DFT) computations to perform a comprehensive search for the stable structures of stoichiometric (WS2)n nano-clusters (n=1-9), within three different exchange-correlation functionals. Our results suggest that n=3, 5, 8 are possible candidates for the low temperature magic sizes of WS2 nano-clusters while at temperatures above 600 Kelvin, n=5 and 7 exhibit higher relative stability among the studied systems. The electronic properties and energy gap of the lowest energy isomers were computed within several schemes, including semilocal PBE and BLYP functionals, hybrid B3LYP functional, many body based DFT+GW approach, and time dependent DFT calculations. Vibrational spectra of the lowest lying isomers, computed by the force constant method, are used to address IR spectra and thermal free energy of the clusters. Time dependent density functional calculation in real time domain is applied to determine the full absorption spectra and optical gap of the lowest energy isomers of the WS2 nano-clusters.