Quantification of finite-temperature effects on adsorption geometries of $\pi$-conjugated molecules

TL;DR

This study combines experimental and theoretical methods to analyze how finite-temperature effects, including vibrational anharmonicity, influence the adsorption geometries of pi-conjugated molecules like azobenzene on metal surfaces.

Contribution

It demonstrates that accounting for vibrational mode anharmonicity is essential for accurately modeling adsorption geometries at finite temperatures.

Findings

Inclusion of substrate screening improves monolayer modeling.

Vibrational anharmonicity significantly affects adsorption geometry.

Explicit vibrational effects are crucial for quantitative agreement.

Abstract

The adsorption structure of the molecular switch azobenzene on Ag(111) is investigated by a combination of normal incidence x-ray standing waves and dispersion-corrected density functional theory. The inclusion of non-local collective substrate response (screening) in the dispersion correction improves the description of dense monolayers of azobenzene, which exhibit a substantial torsion of the molecule. Nevertheless, for a quantitative agreement with experiment explicit consideration of the effect of vibrational mode anharmonicity on the adsorption geometry is crucial.