Ahsin A, Shah AB, Ayub K. Germanium-based superatom clusters as excess electron compounds with significant static and dynamic NLO response; a DFT study.
RSC Adv 2021;
12:365-377. [PMID:
35424493 PMCID:
PMC8978613 DOI:
10.1039/d1ra08192f]
[Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Accepted: 12/04/2021] [Indexed: 11/21/2022] Open
Abstract
Herein, the geometric, electronic, and nonlinear optical properties of excess electron zintl clusters Ge5AM3, Ge9AM5, and Ge10AM3 (AM = Li, Na, and K) are investigated. The clusters under consideration demonstrate considerable electronic stability as well as superalkali characteristics. The NBO charge is transferred from the alkali metal to the Ge-atoms. The FMO analysis shows fabulous conductive properties with a significant reduction in SOMO-LUMO gaps (0.79-4.04 eV) as compared with undoped systems. The designed clusters are completely transparent in the deep UV-region and show absorption in the visible and near-IR region. Being excess electron compounds these clusters exhibit remarkable hyperpolarizability response up to 8.99 × 10-26 esu, where a static second hyperpolarizability (γ o) value of up to 2.15 × 10-30 esu was recorded for Ge9Na5 superatom clusters. The excitation energy is the main controlling factor for hyperpolarizability as revealed from the two-level model study. The electro-optical Pockel's effect and the second harmonic generation phenomenon (SHG) are used to investigate dynamic nonlinear optical features. At a lower applied frequency (=532 nm), the dynamic hyperpolarizability and second hyperpolarizability values are significantly higher for the studied clusters. Furthermore, for the Ge9K5 cluster, the hyper Rayleigh scattering (HRS) increases to 5.03 × 10-26 esu.
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