Understanding the structural transformation, stability of medium-sized neutral and charged silicon clusters.

Li Ping Ding,Peng Shao,Fang Hui Zhang,Xiao Yu Kuang,Jian Lv,Yong Sheng Zhu,Cheng Lu

doi:10.1038/srep15951

Abstract

The structural and electronic properties for the global minimum structures of medium-sized neutral, anionic and cationic Sinμ (n = 20–30, μ = 0, −1 and +1) clusters have been studied using an unbiased CALYPSO structure searching method in conjunction with first-principles calculations. A large number of low-lying isomers are optimized at the B3PW91/6-311 + G* level of theory. Harmonic vibrational analysis has been performed to assure that the optimized geometries are stable. The growth behaviors clearly indicate that a structural transition from the prolate to spherical-like geometries occurs at n = 26 for neutral silicon clusters, n = 27 for anions and n = 25 for cations. These results are in good agreement with the available experimental and theoretical predicted findings. In addition, no significant structural differences are observed between the neutral and cation charged silicon clusters with n = 20–24, both of them favor prolate structures. The HOMO-LUMO gaps and vertical ionization potential patterns indicate that Si22 is the most chemical stable cluster, and its dynamical stability is deeply discussed by the vibrational spectra calculations.

Highlights

The binding energies, highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) energy gaps, vertical ionization potentials, adiabatic detachment energies, polarizability including Raman activities, and infrared intensities are predicted at the B3PW91/6-311 + G* level
(ii) O ur structural optimizations indicate that an appreciable structural transition from prolate to spherical-like geometries occur at n = 2 6 for neutral Sin clusters, n = 2 7 for anions and n = 2 5 for cations
The relative stability analysis is carried out by calculating HOMO-LUMO gaps and vertical ionization potential, which shows that Si22 cluster has higher stability than the neighboring clusters

Summary

Introduction

Despite the enormous progress that has been made, the true lowest-energy structures for the silicon clusters in the size range of 20 ≤ n ≤ 3 0 are still debatable. In order to systematically study the structural evolution and electronic properties of silicon clusters, we here present extensive structure searches to explore the global minimum geometric structures of medium-sized neutral and charged silicon clusters in the size range of 20 ≤ n ≤ 3 0, by combining our developed CALYPSO method with the density functional theory. Our first goal of this work is to gain a fundamental understanding of the ground state geometric structures in medium-sized silicon clusters. We are motivated to explore the physical mechanism of the growth behaviors of medium-sized silicon clusters and provide relevant information for further theoretical and experimental studies.

Methods

Results

Conclusion