Benjamin J. Lynch

Multi-coefficient extrapolated density functional theory for thermochemistry and thermochemical kinetics

We have developed a new kind of multi-coefficient correlation method (MCCM) by empirically mixing correlated wave function methods and density functional methods. The new methods constitute a generalization of hybrid density functional theory and may be called multi-coefficient extrapolated density functional theory. Results by the new methods are compared to those obtained by G3SX, G3SX(MP3), CBS-Q and MCCM/3 for calculations of atomization energies, barrier heights, ionization potentials and electron affinities. These results show that the multi-coefficient extrapolated density functional theory is more accurate for thermochemistry and thermochemical kinetics than the pure wave function methods of comparable cost. As a byproduct of this work we optimized a new hybrid meta density functional theory called TPSS1KCIS, which has excellent performance for thermochemistry.

Tests of second-generation and third-generation density functionals for thermochemical kineticsElectronic supplementary information (ESI) available: Mean errors for pure and hybrid DFT methods. See http://www.rsc.org/suppdata/cp/b3/b316260e/

We report tests of second- and third-generation density functionals, for pure density functional theory (DFT) and hybrid DFT, against the BH6 representative barrier height database and the AE6 representative atomization energy database, with augmented, polarized double and triple zeta basis sets. The pure DFT methods tested are G96LYP, BB95, PBE, mPWPW91, VSXC, HCTH, OLYP, and OPW91 and the hybrid DFT methods tested are B1B95, PBE0, mPW1PW91, B97-1, B98, MPW1K, B97-2, and O3LYP. The performance of these methods is tested against each other as well as against first-generation methods (BP86, BLYP, PW91, B3PW91, and B3LYP). We conclude that the overall performance of the second-generation DFT methods is considerably better than the first-generation methods. The MPW1K method is very good for barrier height calculations, and none of the pure DFT methods outperforms any of the hybrid DFT methods for kinetics. The B1B95, VSXC, B98, OLYP and O3LYP methods perform best for atomization energies. Using a mean mean unsigned error criterion (MMUE) that involves two sizes of basis sets (both with polarization and diffuse functions) and averages mean unsigned errors in barrier heights and in atomization energy per bond, we find that VSXC has the best performance among pure functionals, and B97-2, MPW1K, and B1B95 have the best performance of all hybrid functionals tested.

Obtaining the right orbitals is the first step to calculating accurate binding energies for Cu+ ion

Abstract We investigate the previously reported poor performance of the G2 method for simple copper systems. We optimized CuH + , CuO + , and CuSi + using the HF, MP2, B3LYP, mPW1PW91, and MPW1K methods with three basis sets. We found multiple solutions to the Hartree–Fock equations, which are the cause for previously reported poor behavior of the G2 method. The orbitals of the lowest-energy unrestricted Hartree–Fock solution do not always generate the lowest-energy correlated wavefunction. Hybrid density functional theory methods are shown to be quite successful for obtaining orbitals and for predicting geometries and atomization energies.