Volume 123, Issue 12, 22 September 2005
Index of content:
123(2005); http://dx.doi.org/10.1063/1.2052547View Description Hide Description
The reactions of alkaline earth metal atoms, and , with are studied using a pump-probe technique combined with stimulated Raman pumping and coherent anti-Stokes Raman spectroscopy. For the case, the energy deposited in the level enlarges the bond distance to help facilitate the reaction without opening an additional pathway. For the case, the vibrational excitation of leads to enhancement of the low rotational component of the rotational distribution and the ratio. These results can be predicted with quasi-classical trajectory calculations and interpreted with a kinematic collision model.
Effect of self-interaction error in the evaluation of the bond length alternation in trans-polyacetylene using density-functional theory123(2005); http://dx.doi.org/10.1063/1.2047447View Description Hide Description
The calculation of the bond-length alternation (BLA) in trans-polyacetylene has been chosen as benchmark to emphasize the effect of the self-interaction error within density-functional theory(DFT). In particular, the BLA of increasingly long acetylene oligomers has been computed using the Møller-Plesset wave-function method truncated at the second order and several DFT models. While local-density approximation (LDA) or generalized gradient corrected (GGA) functionals strongly underestimate the BLA, approaches including self-interaction corrections (SIC) provide significant improvements. Indeed, the simple averaged-density SIC scheme (ADSIC), recently proposed by Legrand et al. [J. Phys. B35, 1115 (2002)], provides better results for the structure of large oligomers than the more complex approach of Krieger et al. [Phys. Rev. A45, 101 (1992)]. The ADSIC method is particularly promising since both the exchange-correlation energy and potential are improved with respect to standard LDA/GGA using a physically appealing correction, through a different route than the more popular approach through the Hartree-Fock exchange inclusion within the hybrid functionals.
123(2005); http://dx.doi.org/10.1063/1.2061227View Description Hide Description
It is demonstrated that there is still scope for improvement in the quality of conventional, semiempirical hybrid exchange-correlation functionals in density-functional theory. A new functional, denoted B97-3, is determined from a fit to eight chemical properties (316 data points). For a series of 25 chemical assessments (850 data points) including 17 assessments and 10 chemical properties absent from the fitting data, B97-3 provides the lowest or joint-lowest mean absolute error on 15 occasions, compared to 6, 5, and 4 occasions for B3LYP, PBE0, and B97-2, respectively [A. D. Becke, J. Chem. Phys.98, 5648 (1993);M. Ernzerhof and G. E. Scuseria, J. Chem. Phys.110, 5029 (1999);C. Adamo and V. Barone, J. Chem. Phys.110, 6158 (1999);P. J. Wilson, T. J. Bradley, and D. J. Tozer, J. Chem. Phys.115, 9233 (2001)]. Mean absolute errors from B97-3 are, on average, 21%, 18%, and 12% smaller than from these three functionals. The most notable improvements are obtained for classical reaction barriers, where the error reductions are 60%, 54%, and 27%.
123(2005); http://dx.doi.org/10.1063/1.2046607View Description Hide Description
Numerous vibrational modes of spherical submicrometer particles in fabricated soft opals are experimentally detected by Brillouinlight scattering and theoretically identified by their spherical harmonics by means of single-phonon scattering-cross-section calculations. The particle size polydispersity is reflected in the line shape of the low-frequency modes, whereas lattice vibrations are probably responsible for the observed overdamped transverse mode.