The role of exact‐exchange in the theoretical description of organic‐metal interfaces

Abstract

AbstractWe investigate the ability of different density functional methods to describe the electronic properties of isolated gold clusters, self‐assembled monolayers (SAM) of oligophenylthiols (including the depolarization effect), and the biphenylthiol/gold interface. To elucidate the role of the exchange interaction, we consider a hierarchy of functionals including conventional (e.g., within the gradient corrected approximation), hybrid, and effective exact‐exchange functionals, namely the Localized Hartree–Fock (LHF) method, which is free from the self‐interaction‐error (SIE).We find that conventional exchange‐correlation functionals cannot well describe the energy‐level alignment at the metal/organic interface and predict a negligible metal‐molecule charge‐transfer. In addition, an overestimation of dipole moments and polarization effects are obtained in oligophenylthiols, leading to a wrong description of the SAM depolarization effect. Both limitations are mostly overcome if exact‐exchange contributions are taken into account either using an hybrid functional or the LHF method. In particular, an accurate description of the metal/organic interface is only achieved using SIE free methods. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010