This poster describes a density functional theory (DFT) of electronic excited states that is alternative and complementary to time-dependent DFT (TDDFT).  Our approach is formally exact and originates from a variational formalism.  We show that a quasi‑adiabatic approximation of excited state density functionals leads to a practical computational scheme that we call <i>Orthogonality Constrained DFT</i> (OCDFT).  The advantages of OCDFT consist in: 1) the ability to correctly describe charge-transfer excitations with traditional density functionals, 2) avoidance of variational collapse, and 3) a computational cost that is identical to that of ground state DFT.  Benchmark computations show that OCDFT can be used to predict UV/VIS spectra with error metrics similar to those of TDDFT.  Simulations of X-ray absorption spectra with TDDFT generally yield excitation energies that have errors in the excess of 10–20 eV.  On the contrary, we will show that for this class of excited states OCDFT yields excitation energies in excellent agreement with experiments, with an average error of about 1 eV.  The power of OCDFT will be showcased in computations of the X-ray absorption spectrum of adenine and thymine.

Simulating X-ray, UV, and VIS absorption spectra with orthogonality constrained density functional theory

249th National Meeting (2015)

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