# Energy Level Alignment at Molecule-Metal Interfaces from an Optimally-Tuned Range-Separated Hybrid Functional

## TL;DR

This paper introduces a new computational method using optimally-tuned range-separated hybrid functionals to accurately predict energy level alignment at molecule-metal interfaces, improving upon traditional density functional theory approaches.

## Contribution

The authors develop a self-consistent, non-empirical scheme that captures surface polarization effects for precise electronic structure calculations of molecule-metal interfaces.

## Key findings

- Quantitative agreement with experimental level alignments
- Accurate prediction of work function changes
- Effective for both physisorbed and chemisorbed systems

## Abstract

The alignment of the frontier orbital energies of an adsorbed molecule with the substrate Fermi level at metal-organic interfaces is a fundamental observable of significant practical importance in nanoscience and beyond. Typical density functional theory calculations, especially those using local and semi-local functionals, often underestimate level alignment leading to inaccurate electronic structure and charge transport properties. In this work, we develop a new fully self-consistent predictive scheme to accurately compute level alignment at certain classes of complex heterogeneous molecule-metal interfaces based on optimally-tuned range-separated hybrid functionals. Starting from a highly accurate description of the gas-phase electronic structure, our method by construction captures important nonlocal surface polarization effects via tuning of the long-range screened exchange in a range-separated hybrid in a non-empirical and system-specific manner. We implement this functional in a plane-wave code and apply it to several physisorbed and chemisorbed molecule-metal interface systems. Our results are in quantitative agreement with experiments, both the level alignment and work function changes. Our approach constitutes a new practical scheme for accurate and efficient calculations of the electronic structure of molecule-metal interfaces.