Structure, Bonding, and Relative Stability of the Ground and Low-Lying Electronic States of CuO₂. The Role of Exact Exchange

Abstract

The C(2v) and C(s) ground and low-lying states of doublet CuO2 are examined for a series of different density functionals (pure, hybrid, and meta-hybrid) and CCSD(T) methods. The effect of changing the B3LYP functional a0 parameter is also explored. CCSD(T) results at the complete basis set limit show that the relative stability of the different electronic states is 2A(2)(C(2v)) < 2A''(Cs) < 2B(2)(C(2v)) < 2A'(C(s)) 2A(1)(C(2v)) < 2B(1)(C(2v)). Unlike CCSD(T), all DFT methods analyzed in this work erroneously predict the end-on 2A'' state as the ground state for CuO2 irrespective of the type of functional and percentage of Hartree-Fock (exact) exchange included in the B3LYP-like functional. Among the different functionals tested, B3LYP gives the best geometries and relative energies for the different electronic states when compared to CCSD(T) results. As for the effect of the a0 parameter, it is found that the B3LYP-like functional yielding better geometries contains 20% of exact exchange, although somewhat unexpectedly, the B3LYP-like functional with a larger contribution of exact exchange (90%) is the one that gives the smaller standard deviation for relative energies.

Density Functional Calculation of the Structure and Electronic Properties of CunOn (n = 1−8) Clusters

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Computational modelling of oxygenation processes in enzymes and biomimetic model complexes

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Absorption and fluorescence properties of oligothiophene biomarkers from long-range-corrected time-dependent density functional theory

“…In these hybrid DFT benchmarks, we fixed a x = 1 À a 0 in eqn (1) but kept the correlation contribution with a c = 0.81 unchanged. The a x = 1 À a 0 convention is already a common choice used in many hybrid functionals [56][57][58][59] such as Becke's B1 convention 57 (in a separate study, we carried out calculations with a x fixed to the original 0.72 value recommended by Becke and found that the error in excitation energies was larger by 0.02 eV compared to the a x = 1 À a 0 convention). It is also worth noting that the set of parameters a 0 = 0.5 and a x = 1 À a 0 = 0.5 yields a functional similar to the BHHLYP functional (a c = 0) with the exception that our choice has an extra correlation contribution due to the DE c,LYP term.…”