Interaction of Alkylamines with Cu Surfaces: A Metal-Organic Many-Body Force Field

Hexadecylamine (HDA) and alkylamines, in general, are key molecules in the shape-selective synthesis of Cu nanostructures. To resolve certain aspects of these syntheses, we develop a classical many-body force field to describe the interactions of HDA with Cu surfaces. We parametrize the force field through force and energy matching to results from first-principles density functional theory (DFT). Our force field reproduces the DFT binding energies and configurations of self-assembled HDA layers on Cu(100) and Cu(111) at various coverages. We implemented the force field in classical molecular dynamics (MD) simulations to resolve various HDA self-assembled-layer structures on Cu(100) in vacuum, and we find that HDA layers undergo a continuous structural transition through various ordered layers at high coverage to disordered layers at lower coverages. We probed pentylamine (PA), decylamine (DA), and HDA binding on Cu surfaces in vacuum with MD and find that DA forms self-assembled layers, but PA layers disorder at experimental temperatures. We investigated HDA monolayers on Cu surfaces in an aqueous medium with MD and found that the self-assembled monolayer structure in vacuum is retained. The long and hydrophobic alkyl tails in the self-assembled HDA monolayer repel water molecules and would prevent Cu oxidation, which agrees with experiment.