title: Simulation of X-ray absorption spectra with orthogonality constrained density functional theory.
abstract: Orthogonality constrained density functional theory (OCDFT) [F. A. Evangelista, P. Shushkov and J. C. Tully, J. Phys. Chem. A, 2013, 117, 7378] is a variational time-independent approach for the computation of electronic excited states. In this work we extend OCDFT to compute core-excited states and generalize the original formalism to determine multiple excited states. Benchmark computations on a set of 13 small molecules and 40 excited states show that unshifted OCDFT/B3LYP excitation energies have a mean absolute error of 1.0 eV. Contrary to time-dependent DFT, OCDFT excitation energies for first- and second-row elements are computed with near-uniform accuracy. OCDFT core excitation energies are insensitive to the choice of the functional and the amount of Hartree-Fock exchange. We show that OCDFT is a powerful tool for the assignment of X-ray absorption spectra of large molecules by simulating the gas-phase near-edge spectrum of adenine and thymine.
authors.affiliation: Department of Chemistry and Cherry L. Emerson Center for Scientific Computation, Emory University, Atlanta, Georgia 30322, USA. francesco.evangelista@emory.edu.
authors.forename: Wallace D
authors.initials: WD
authors.lastname: Derricotte
authors.forename: Francesco A
authors.initials: FA
authors.lastname: Evangelista
mesh_terms: D065638:Absorption, Radiation; D000225:Adenine / Q000737:chemistry* / Q000528:radiation effects; D003198:Computer Simulation; D008956:Models, Chemical; D008958:Models, Molecular; D011789:Quantum Theory; D013941:Thymine / Q000737:chemistry* / Q000528:radiation effects; D056928:X-Ray Absorption Spectroscopy / Q000379:methods*; D014965:X-Rays
chemical_list: D000225:Adenine; D013941:Thymine