Orthogonality constrained density functional theory (OCDFT) [F. A. Evangelista, P. Shushkov and J. C. Tully, J. Phys. Chem. A, 2013, 117, 7378] is a method for calculating electronic excited states that builds upon a variational time-independent approach. OCDFT was previously benchmarked on a test set of core excitations from small gas-phase molecules and shown to be a powerful tool to compute the excitation energies of core-electrons with remarkable quantitative accuracy. [W. D. Derricotte, F. A. Evangelista Phys. Chem. Chem. Phys, 2015, 17, 14360] In this work we present an extension to OCDFT, applying a restricted excitation window (REW) which effectively controls the excitation space to only consider transitions from occupied orbitals of interest in a given system. Within the framework of orthogonally constrained excited states, this enables the efficient calculation of core-excited states in molecules adsorbed to surfaces and systems solvated with explicit solvent molecules. REW-OCDFT is tested by calculating the near-edge x-ray absorption spectra of small organic molecules chemisorbed on a silicon surface and the carbon K-edge of CO2 and carbonic acid (H2CO3).

Restricted excitation window orthogonality constrained density functional theory: Application to the near-edge x-ray absorption spectra of chemisorbed and solvated molecules

251st National Meeting (2016)

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