title: Many-body Green's function GW and Bethe-Salpeter study of the optical excitations in a paradigmatic model dipeptide.
abstract: We study within the many-body Green's function GW and Bethe-Salpeter formalisms the excitation energies of a paradigmatic model dipeptide, focusing on the four lowest-lying local and charge-transfer excitations. Our GW calculations are performed at the self-consistent level, updating first the quasiparticle energies, and further the single-particle wavefunctions within the static Coulomb-hole plus screened-exchange approximation to the GW self-energy operator. Important level crossings, as compared to the starting Kohn-Sham LDA spectrum, are identified. Our final Bethe-Salpeter singlet excitation energies are found to agree, within 0.07 eV, with CASPT2 reference data, except for one charge-transfer state where the discrepancy can be as large as 0.5 eV. Our results agree best with LC-BLYP and CAM-B3LYP calculations with enhanced long-range exchange, with a 0.1 eV mean absolute error. This has been achieved employing a parameter-free formalism applicable to metallic or insulating extended or finite systems.
authors: Institut Néel, CNRS and Université Joseph Fourier, B.P. 166, 38042 Grenoble Cedex 09, France.
authors: C
authors: C
authors: Faber
authors: P
authors: P
authors: Boulanger
authors: I
authors: I
authors: Duchemin
authors: C
authors: C
authors: Attaccalite
authors: X
authors: X
authors: Blase
mesh_terms: D004151:Dipeptides / Q000737:chemistry*; D008958:Models, Molecular; D055620:Optical Phenomena; D011789:Quantum Theory
chemical_list: D004151:Dipeptides