The electronic structure of Pd-3 and Pt-3 clusters and the detailed reaction mechanism of activation of H-2 and CH4 on these clusters have been studied with a density functional method. Full geometry optimization has been carried out and led to the reaction mechanisms that are dramatically different from those of a previous work where only limited potential energy scans were carried out. In the Pd-3 + H-2 system, Pd-3, like Pd-2, activates H-2 without barrier. For the activation of the C-H bond in CH4 with Pd-3, although the final products are found to be similar in energy compared to the case of Pd-2, the activation barriers on Pd-3 are much higher than those on Pd-2. This difference has been explained in terms of the large repulsion from the s(1)d(9) configurations of Pd atoms in Pd-3, whereas Pd atoms in Pd-2 adopt mainly the less repulsive d(10) configuration. In the case of Pt-3 + H-2/CH4, the reactions basically follow the same pattern as in the Pt-2 systems. Namely H-H and C-H are broken at first on a single Pt atom, and then one H atom migrates to other Pt atom(s). No activation barrier has been found on either the singlet or the triplet state for H-H activation, and a smaller activation barrier height compared to the Pt-2 case has been obtained for the C-H activation. Results from the current series of studies are consistent with the recent experimental observations on the reactivities of unsupported Pd-n and Pt-n.
%0 Journal Article
%1 hlwoodcock:Q.1998c
%A Cui, Q.
%A Musaev, D. G.
%A Morokuma, K.
%D 1998
%J J. Phys. Chem. A
%K atoms dehydrogenation basis functions gaussian theory energies electronic-structure density-functional first-row atomic platinum sets dynamics bibtex-import clusters cations
%N 31
%P 6373--6384
%T Molecular orbital study of h-2 and ch4 activation on small metal clusters. 2. pd-3 and pt-3
%V 102
%X The electronic structure of Pd-3 and Pt-3 clusters and the detailed reaction mechanism of activation of H-2 and CH4 on these clusters have been studied with a density functional method. Full geometry optimization has been carried out and led to the reaction mechanisms that are dramatically different from those of a previous work where only limited potential energy scans were carried out. In the Pd-3 + H-2 system, Pd-3, like Pd-2, activates H-2 without barrier. For the activation of the C-H bond in CH4 with Pd-3, although the final products are found to be similar in energy compared to the case of Pd-2, the activation barriers on Pd-3 are much higher than those on Pd-2. This difference has been explained in terms of the large repulsion from the s(1)d(9) configurations of Pd atoms in Pd-3, whereas Pd atoms in Pd-2 adopt mainly the less repulsive d(10) configuration. In the case of Pt-3 + H-2/CH4, the reactions basically follow the same pattern as in the Pt-2 systems. Namely H-H and C-H are broken at first on a single Pt atom, and then one H atom migrates to other Pt atom(s). No activation barrier has been found on either the singlet or the triplet state for H-H activation, and a smaller activation barrier height compared to the Pt-2 case has been obtained for the C-H activation. Results from the current series of studies are consistent with the recent experimental observations on the reactivities of unsupported Pd-n and Pt-n.
@article{hlwoodcock:Q.1998c,
abstract = {The electronic structure of Pd-3 and Pt-3 clusters and the detailed reaction mechanism of activation of H-2 and CH4 on these clusters have been studied with a density functional method. Full geometry optimization has been carried out and led to the reaction mechanisms that are dramatically different from those of a previous work where only limited potential energy scans were carried out. In the Pd-3 + H-2 system, Pd-3, like Pd-2, activates H-2 without barrier. For the activation of the C-H bond in CH4 with Pd-3, although the final products are found to be similar in energy compared to the case of Pd-2, the activation barriers on Pd-3 are much higher than those on Pd-2. This difference has been explained in terms of the large repulsion from the s(1)d(9) configurations of Pd atoms in Pd-3, whereas Pd atoms in Pd-2 adopt mainly the less repulsive d(10) configuration. In the case of Pt-3 + H-2/CH4, the reactions basically follow the same pattern as in the Pt-2 systems. Namely H-H and C-H are broken at first on a single Pt atom, and then one H atom migrates to other Pt atom(s). No activation barrier has been found on either the singlet or the triplet state for H-H activation, and a smaller activation barrier height compared to the Pt-2 case has been obtained for the C-H activation. Results from the current series of studies are consistent with the recent experimental observations on the reactivities of unsupported Pd-n and Pt-n.},
added-at = {2006-06-16T05:03:46.000+0200},
author = {Cui, Q. and Musaev, D. G. and Morokuma, K.},
biburl = {https://www.bibsonomy.org/bibtex/26e4882433cebf06a3bf6c1633d8a4547/hlwoodcock},
citeulike-article-id = {569414},
comment = {108QT J PHYS CHEM A},
interhash = {0a6eb8ed0dd5270986b33614d526fa84},
intrahash = {6e4882433cebf06a3bf6c1633d8a4547},
journal = {J. Phys. Chem. A},
keywords = {atoms dehydrogenation basis functions gaussian theory energies electronic-structure density-functional first-row atomic platinum sets dynamics bibtex-import clusters cations},
number = 31,
pages = {6373--6384},
priority = {2},
timestamp = {2006-06-16T05:03:46.000+0200},
title = {Molecular orbital study of h-2 and ch4 activation on small metal clusters. 2. pd-3 and pt-3},
volume = 102,
year = 1998
}