Systematic investigation of structure and optoelectronic properties of Gen (n=3-20), MGe9 (M = Ga, Si, Sn, As) and GaxGe(10-x) (x=1-10) Clusters: Computational approach

Herein, the structural, electronic, and optical properties of Ge-n (n = 3-20), mixed MGe9 (M = Ga, Si, Sn, As), and GaxGe(10-x) (x = 1-10) clusters using the density-functional theory (DFT) and the time dependentDFT (TD-DFT) were systematically investigated. The calculated values of binding energies (E-b, eV/atom), second-order differences of total energies (Delta E-2), and fragmentation energies (E-frg) for pristine Ge-n clusters demonstrated that the pristine Ge-10 and Ge-20 are the most stable structure of Ge-n clusters. Based on first-principles calculations, the properties of studied clusters are highly dependent on their composition. The electronic properties of Ge-n clusters reveal that, in general, the HOMO-LUMO energy gap decreases with increasing the cluster size. SiGe9 was found to be more thermodynamically and chemically stable than its parent. On the other hand, generally, the energy gap of mixed MGe9 clusters decreased compared with the pure Ge-10 cluster. The calculated H-L energy gap of GaxGe((10-x)) (x = 1-10) cluster with even/odd number of Ga atom is in the range of similar to 1.567-2.194 eV/1.153-1.297 eV. Based on TD-DFT calculations, with increasing the cluster size, the maximum wavelength for Ge-n (n = 3-20) clusters shifted towards higher values. Due to their significant optical HOMO-LUMO energy gap and maximum wavelength, these clusters could be potentially promising candidates for optoelectronic devices. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

By systematically investigating the properties of Ge-n, mixed MGe9, and GaxGe(10-x) clusters using DFT and TD-DFT, it was found that the clusters' properties are highly dependent on their composition, with the HOMO-LUMO energy gap decreasing as the cluster size increases. The maximum wavelength for Ge-n clusters also shifts towards higher values as the cluster size increases, making them potential candidates for optoelectronic devices.