1,651 research outputs found
How Large is the Elephant in the Density Functional Theory Room?
A recent paper compares density functional theory results for atomization
energies and dipole moments using a multi-wavelet based method with traditional
Gaussian basis set results, and concludes that Gaussian basis sets are
problematic for achieving high accuracy. We show that by a proper choice of
Gaussian basis sets they are capable of achieving essentially the same accuracy
as the multi-wavelet approach, and identify a couple of possible problems in
the multi-wavelet calculations
Candidate eco-friendly gas mixtures for MPGDs
Modern gas detectors for detection of particles require F-based gases for optimal performance.Recent regulations demand the use of environmentally unfriendly F-based gases t o be limited or banned. This review studies properties of potential eco-friendly gas candidate replacements
Conformations of N-Heterocyclic Carbene Ligands in Ruthenium Complexes Relevant to Olefin Metathesis
The structure of ruthenium-based olefin metathesis catalyst 3 and model π-complex 5 in solution and in the solid state are reported. The N-tolyl ligands, due to their lower symmetry than the traditional N-mesityl substituents, complicate this analysis, but ultimately provide explanation for the enhanced reactivity of 3 relative to standard catalyst 2. The tilt of the N-tolyl ring provides additional space near the ruthenium center, which is consistent with the enhanced reactivity of 3 toward sterically demanding substrates. Due to this tilt, the more sterically accessible face bears the two methyl substituents of the N-aryl rings. These experimental studies are supported by computational studies of these complexes by DFT. The experimental data provides a means to validate the accuracy of the B3LYP and M06 functionals. B3LYP provides geometries that match X-ray crystal structural data more closely, though it leads to slightly less (0.5 kcal mol^(−1)) accuracy than M06 most likely because it underestimates attractive noncovalent interactions
Broken-Symmetry Unrestricted Hybrid Density Functional Calculations on Nickel Dimer and Nickel Hydride
In the present work we investigate the adequacy of broken-symmetry
unrestricted density functional theory (DFT) for constructing the potential
energy curve of nickel dimer and nickel hydride, as a model for larger bare and
hydrogenated nickel cluster calculations. We use three hybrid functionals: the
popular B3LYP, Becke's newest optimized functional Becke98, and the simple
FSLYP functional (50% Hartree-Fock and 50% Slater exchange and LYP
gradient-corrected correlation functional) with two basis sets: all-electron
(AE) Wachters+f basis set and Stuttgart RSC effective core potential (ECP) and
basis set.
We find that, overall, the best agreement with experiment, comparable to that
of the high-level CASPT2, is obtained with B3LYP/AE, closely followed by
Becke98/AE and Becke98/ECP. FSLYP/AE and B3LYP/ECP give slightly worse
agreement with experiment, and FSLYP/ECP is the only method among the ones we
studied that gives an unaceptably large error, underestimating the dissociation
energy of nickel dimer by 28%, and being in the largest disagreement with the
experiment and the other theoretical predictions.Comment: 17 pages, 7 tables, 7 figures; submitted to J. Chem. Phys.;
Revtex4/LaTeX2e. v2 (8/5/04): New (and better) ECP results, without charge
density fitting (which was found to give large errors). Subtracted the
relativistic corrections from all experimental value
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