Reliable energy level alignment at physisorbed molecule-metal interfaces from density functional theory.
A key quantity for molecule-metal interfaces is the energy level alignment of molecular electronic states with the metallic Fermi level. We develop and apply an efficient theoretical method, based on density functional theory (DFT) that can yield quantitatively accurate energy level alignment information for physisorbed metal-molecule interfaces. The method builds on the "DFT+Σ" approach, grounded in many-body perturbation theory, which introduces an approximate electron self-energy that corrects the level alignment obtained from conventional DFT for missing exchange and correlation effects associated with the gas-phase molecule and substrate polarization. Here, we extend the DFT+Σ approach in two important ways: first, we employ optimally tuned range-separated hybrid functionals to compute the gas-phase term, rather than rely on GW or total energy differences as in prior work; second, we use a nonclassical DFT-determined image-charge plane of the metallic surface to compute the substrate polarization term, rather than the classical DFT-derived image plane used previously. We validate this new approach by a detailed comparison with experimental and theoretical reference data for several prototypical molecule-metal interfaces, where excellent agreement with experiment is achieved: benzene on graphite (0001), and 1,4-benzenediamine, Cu-phthalocyanine, and 3,4,9,10-perylene-tetracarboxylic-dianhydride on Au(111). In particular, we show that the method correctly captures level alignment trends across chemical systems and that it retains its accuracy even for molecules for which conventional DFT suffers from severe self-interaction errors.
†Department of Materials and Interfaces, Weizmann Institute of Science, Rehovoth 76100, Israel.
David A
DA
Egger
‡Molecular Foundry and Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
Zhen-Fei
ZF
Liu
‡Molecular Foundry and Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.|§Department of Physics, University of California, Berkeley, California 94720, United States.|∥Kavli Energy Nanosciences Institute at Berkeley, Berkeley, California 94720, United States.
Jeffrey B
JB
Neaton
†Department of Materials and Interfaces, Weizmann Institute of Science, Rehovoth 76100, Israel.
Leeor
L
Kronik
Molecule−metal interface; density functional theory; energy level alignment; image plane; range-separated hybrid