A DFT study of the chemical and optical properties of 7-atom Ag–X [X = Li, Na] nanoalloys for potential applications in opto-electronics and catalysis

Abstract

In this paper, Ag atoms are substituted by X (Li, Na) atoms to form Ag_mX_(7−m) clusters to explore their electronic, chemical and optical properties in the framework of density functional theory (DFT). The clusters are geometrically optimized without imposing symmetry and later, vibrational analysis is carried out to test the stability of the optimized structures. The calculation of ionization potential and electron affinity asserted that the Li and Na doped bimetallic clusters (especially, Ag₄Li₃ and Ag₃Li₄) are very stable in the neutral state, but their anions are expected to be very reactive. The calculated absorption spectra of the Ag_mX_7−m clusters have revealed that the doping of Li and Na has made the absorption band wider with regards to undoped Ag₇ clusters. Therefore, this work suggests that Li and Na doping (especially, Ag₄X₃, Ag₃X₄ and Ag₂X₅ clusters) will result in improvement of the absorption band in the 1–5 eV range, which is the prime absorption band for opto-electronic devices such as solar cells.