Effect of gold slab layers relaxation on adsorption of alkanethiols on the (111) surface: a density functional theory study.

CONTEXT

Despite numerous studies on alkanethiol adsorption on gold surfaces, this work uniquely investigates the impact of Au(111) surface layers relaxation on adsorption energy, electrical conductivity, and molecular geometry using density functional theory (DFT). We demonstrate that adsorption energy increases linearly with increasing relaxation layers. Notably, relaxing only the top layer yields a slope close to experimental data. Geometrically, molecules exhibit greater tilt on a fully frozen surface, except methanethiol. In terms of electrical conductivity, gap energy decreases upon adsorption when all layers are frozen. Furthermore, Fermi energy rises exponentially with adsorption energy for a frozen surface but follows a linear trend with relaxation. These insights offer a deeper understanding of surface effects on molecular adsorption.

METHODS

Adsorption energies and geometric parameters were calculated by DFT with QUANTUM ESPRESSO, using GGA-PBE and Grimme D3 for van der Waals corrections. Core-valence interactions were described by PAW and pseudopotentials. Au(111) slab, constructed with VESTA, contained 3 layers.