Investigation of Electronic and Molecular Features of Zn3S3/PEG4000 Nano-Composite Using the DFT Method

Abstract

Molecular geometry structures were accurately optimized to low convergence energy thresholds for the Zn3S3 cluster before and after adding Polyethylene Glycol (PEG4000). Density functional theory DFT/ B3LYP calculations with 6-113G (d, p) basis set were employed to investigate structural and electronic properties of Zn3S3/PEG4000 composite. The FTIR spectral lines were analyzed where an agreement of FTIR spectra of titled molecules was evaluated between experimental and theoretical findings of the active peaks of O–H, C–H, C=O, C–O–C, and Zn–S functional groups. The vibrational modes frequencies were systematically analyzed on the distribution basis of potential energy around the range 0–4000 cm-1 and observed 12 modes of vibrations for the Zn3S3 molecule, while 36 modes for the Zn3S3/PEG4000 compound. Frontier high occupied, and low unoccupied molecular orbitals (HOMO&LUMO) were calculated and plotted to obtain the energy gap (E𝒈) resulting from the difference between those orbitals. The promising indicator was obtained at increasing E𝒈 from (4.031 to 4.459) eV after adding PEG4000, pointing out the effect of polymer on the ZnS surface as a capping agent. Additionally, electronic features of the mentioned structures, such as IP, EA, Ef, E𝒈, 𝐶𝑝, χ, η, Ѕ, and ω, were calculated. Finally, the molecular electrostatic potential (MEP) diagram of Zn3S3 and Zn3S3/ PEG4000 and charge densities of isosurface and contour diagrams were estimated, showing the nucleophilic and electrophilic attack of these compounds.