Biomedical subjects

Nick X Wang

Publications and source records attributed to Nick X Wang.

3 recordsLinked to original sources

PubMed2006

Behavior of density functionals with respect to basis set. 3. Basis set superposition error.

The impact of basis set superposition error (BSSE) upon molecular properties determined using the density functionals B3LYP, B3PW91, B3P86, BLYP, BPW91, and BP86 in combination with the correlation consistent basis sets [cc-pVnZ, where n = D(2), T(3), Q(4), and 5] for a set of first-row closed-shell molecules has been examined. Correcting for BSSE enables the irregular convergence behavior in molecular properties such as dissociation energies with respect to increasing basis set size, noted in earlier studies, to be improved. However, for some molecules and functional combinations, BSSE correction alone does not improve the irregular convergence behavior.

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PubMed2005

Density functional theory and the correlation consistent basis sets: the tight d effect on HSO and HOS.

The HSO and HOS isomers have been revisited using the DFT functionals, B3LYP, B3PW91, and PBE, in combination with tight d-augmented correlation consistent basis sets, cc-pV(x+d)Z and aug-cc-pV(x+d)Z for second-row atoms. Structures, vibrationally averaged structures, relative energies, harmonic and anharmonic frequencies, enthalpies of formation of HSO and HOS, and the barrier for the HSO/HOS isomerization have been determined. These results were compared with results from previous DFT and ab initio studies in which the standard correlation consistent basis sets were used. The relative energies of the two isomers converge more rapidly and smoothly with respect to increasing basis set size for the tight d-augmented sets than for the standard basis sets. Our best calculations, B3PW91/aug-cc-pV(5+d)Z, for the relative energy of the isomers are in excellent agreement with previous CCSD(T) results given by Wilson and Dunning.

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PubMed2004

The behavior of density functionals with respect to basis set. I. The correlation consistent basis sets.

The accuracy of density functional theory in the description of geometries and atomization energies has been assessed by comparison to experimental data for a series of first-row closed-shell molecules. Six commonly used functionals (B3LYP, B3PW91, B3P86, BLYP, BPW91, BP86) were investigated in combination with the correlation-consistent basis sets [cc-pVxZ and aug-cc-pVxZ where x=D(2), T(3), Q(4), 5]. The convergence of molecular properties with respect to increasing basis set size has been examined. A full statistical error analysis has been performed, assessing the success of each functional with respect to each basis set in terms of both accuracy and precision. Overall, there is smooth convergence towards the Kohn-Sham limit for the hybrid functionals B3LYP and B3PW91, whereas the nonlocal functionals are relatively insensitive to basis set choice.

Journal Article↗