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Energy Level Alignment at Hybridized Organic-Metal Interfaces: The Role of Many-Electron Effects
Y. Chen, I. Tamblyn, and S.Y. Quek Journal of Physical Chemistry C, 121, 24, 13125-13134 (2017) The energy level alignment of frontier molecular levels relative to the metal Fermi level is critical to the conductance and functionality of molecular electronic devices, yet comprehensive understanding of many-electron effects at these interfaces has been lacking. In this work, we employ GW calculations -- a state-of-the-art computational approach for capturing electron correlation effects -- to examine eleven different geometries of molecules chemisorbed on gold surfaces, benchmarking against photoemission data from benzene-diamine monolayers on Au(111). We find that frontier molecular levels undergo substantial renormalization of approximately 1.5 eV beyond simple image charge screening effects. For weakly chemisorbed systems such as amines and pyridines on gold, the level shifts arise from screened exchange energy alone, suggesting simpler computational alternatives are viable. In contrast, for strongly chemisorbed systems such as thiolates, dynamic screening effects become significant and require more sophisticated treatment. These results constitute an important step towards the understanding and manipulation of functional molecular and organic systems for both fundamental studies and applications. |
