Comprehensive DFTB Parametrization and Its Utilization as a Preoptimizer for Investigating Au-Nanostructures + H2O Systems.

Abstract

A novel parameterization of a self-consistent charge density functional-based tight-binding scheme (SCC-DFTB) to characterize gold (Au)-water hybrid systems by developing new pair parameters for (Au, O, H-X where X = Au, O, H) using the DFTB module of Material Studio 2020 is introduced. To characterize Au-water systems within the DFTB framework, the derived parameters are systematically compared with DFT-DMOL3 and DFTB-AuOrg (existing library of DFTB) data for Au_n clusters (n = 2, 4, 8, 25, and 34), Au_n mono layer surfaces (n = 7, 19, 25, 37, and 49), Au₅₀ bilayer surface, and Au nanostructures-H₂O complexes. The geometrical, energetic, and electronic characteristics derived from the newly parametrized library (DFTB-AuOH) for the Au clusters align well with both the DFT-DMOL3 and the DFTB-AuOrg results, demonstrating that the stability of the Au clusters is accurately represented by the existing parameters. The structural outcomes derived from the DFTB-AuOH for Au surfaces indicate its substantial capability to optimize extensive gold surfaces in comparison to the DFT-DMOL3 approach, in which, in this case, the DFTB-AuOrg approach identified bent surfaces as the optimized configurations. Furthermore, the structural and energetic achievements determined from the DFTB-AuOH for Au nanostructure complexes with water molecule(s) reveal low-energy configurations and optimized structures with minimal variation when compared to DFT-DMOL3. The linear correlation equations of Y = (-0.044) X - 10.198 and Y = (-0.05) X - 10.538 are applied to the adsorption and interaction energy, respectively, to scale these DFTB-AuOH energies to their corresponding DFT-DMOL3 energies and to investigate all these energies in relation to the gold surface size, thereby confirming these accomplishments and demonstrating their compatibility significantly. The activation energy of water dissociation on Au surfaces is compared through all three approaches, and it also demonstrates significant compatibility as well. Lastly, the study of the molecular dynamics simulations reveals significant variations in the expected dynamic behavior among the DFTB-AuOH, DFT-DMOL3, and DFTB-AuOrg techniques. DFTB-AuOH consistently exhibits variations that more closely align with DFT-DMOL3, albeit of lesser magnitude, in contrast to DFTB-AuOrg, which predicts significantly smaller fluctuations overall.