Theoretical studies of the dynamics of the abstraction reaction, H' + HBr (v=0,j=0) --> H'H + Br, have been performed with quasiclassical trajectory method (QCT) on a new ab initio potential energy surface (Y. Kurosaki and T. Takayanagi, private communication). The calculated QCT cross sections are in good agreement with earlier quantum wave packet results over most of the collision energy range from 0.1 to 2.6 eV, and the state-resolved rotational distributions of the product H'H molecule are quantitatively consistent with the experimental results. Comparisons of the QCT-calculated rotational-state-resolved cross sections on different potential energy surfaces show that the characteristics of the potential energy surface in the region far away from the minimum energy path have a large influence on the title abstraction reaction dynamics, and the indirect reactions that do not follow the minimum energy path have little influence on the differential cross sections (DCS). The DCSs are mainly governed by the direct reactions that do follow the minimum energy path, at both low and high collision energies. The degree of the rotational alignment of the product H'H molecule is strong at high collision energies, which means that the influence of the indirect reactions on the product rotational alignment is negligible, whereas the distribution of P(varphi(r)) is sensitive to the indirect reactions at high collision energies. With increasing collision energy, the polarization of the product rotational angular momentum decreases and the molecular rotation of the product prefers an in-plane reaction mechanism rather than the out-of-plane mechanism.

Ruthenium clusters of up to 64 atoms were studied using density-functional theory with a plane wave basis set. The simple cubic structure was found to be the most stable structure in the formation of small ruthenium clusters. A strong trend of trimer formation was also observed in the linear ruthenium clusters. All the ruthenium clusters investigated in this work are ferromagnetic with large magnetic moments and have small energy gaps between the highest occupied and the lowest unoccupied molecular orbitals. A quantitative correlation was established between the energetic, electronic, and magnetic properties of ruthenium clusters and the cluster size and structure. Our analysis showed that the atoms in similar bonding environments have similar binding energies. On the basis of this analysis, estimations were made on the binding energy for certain planar and simple cubic ruthenium clusters. The estimated binding energies are in good agreement with those from the density-functional theory calculations.

A systematic investigation of palladium nanoparticles of up to 55 atoms (1.4 nm) has been conducted using density functional theory with a plane wave basis set. The stability of these nanoparticles increases with cluster size and dimensionality. It also depends strongly on the cluster structures through two factors, the coordination numbers of atoms and the strength of the single bonds. Both the energy gap between the highest occupied and the lowest unoccupied molecular orbitals and the magnetic moment change oscillatorily with cluster size. Furthermore, highly magnetic clusters tend to have large energy gaps. Analysis of the atom-resolved magnetic moment reveals that the local magnetism of a cluster depends mainly on the atomic bonding environments. A simple approach is proposed to predict relative stabilities of various structures for larger clusters. In addition, a structure factor is defined to correlate quantitatively various properties of the Pd clusters with their structures.