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Recalibrated Double Many-Body Expansion Potential Energy Surface and Dynamics C...
Caridade, P. J. S. B.; Poveda, L. A.; Rodrigues, S. P. J.; Varandas, A. J. C.A single-sheeted double many-body expansion potential energy surface is reported for the lowest doublet state of HN2 by fitting additional multireference configuration interaction energies in the N···NH channel. A stratified analysis of the root-mean-squared error indicates an accuracy superior to that achieved for the previously reported form. Detailed dynamical tests are also performed for the N + NH reaction...
New Double Many-Body Expansion Potential Energy Surface for Ground-State HCN fr...
Varandas, A. J. C.; Rodrigues, S. P. J.An accurate single-sheeted double many-body expansion potential energy surface has been obtained for the ground electronic state of the hydrogen cyanide molecule via a multiproperty fit to ab initio energies and rovibrational data. This includes 106 rovibrational levels and 2313 discrete points, which are fit with a rmsd of 4 cm-1 and 2.42 kcal mol-1, respectively, and seven zero first-derivatives that are repr...
Unimolecular and Bimolecular Calculations for HN2
Caridade, P. J. S. B.; Rodrigues, S. P. J.; Sousa, F.; Varandas, A. J. C.Using a recently reported double many-body expansion potential energy surface, quasi-classical, statistical mechanics, and quantum resonance calculations have been performed for the HN2 system by focusing on the determination of bimolecular (N + NH and H + N2) and unimolecular (decomposition of HN2) rate constants as well as the relevant equilibrium constants. ; http://dx.doi.org/10.1021/jp045102g
Dynamics Study of the Reaction S + O2 → SO + O and Its Reverse on a Single-Valu...
Rodrigues, S. P. J.; Varandas, A. J. C.Quasiclassical trajectory calculations have been carried out for the reaction S + O2 → SO + O and its reverse using an accurate single-valued double many-body expansion (DMBE) potential energy surface previously reported for the ground electronic state of the sulfur dioxide molecule. A new scheme is suggested for thermalization of the reactants which avoids the usual separation of rotation and vibration. A deta...
A realistic double many-body expansion potential energy surface for from a mul...
Varandas, A. J. C.; Rodrigues, S. P. J.A single-valued double many-body expansion potential energy surface (DMBE I) recently obtained for the ground electronic state of the sulfur dioxide molecule by fitting correlated ab initio energies suitably corrected by scaling the dynamical correlation energy is now refined by fitting simultaneously available spectroscopic levels up to 6886 cm-1 above the minimum. The topographical features of the novel poten...
Single-Valued Double Many-Body Expansion Potential Energy Surface of Ground-Sta...
Rodrigues, S. P. J.; Sabín, J. A.; Varandas, A. J. C.An accurate single-valued double many-body expansion potential energy surface has been obtained for the ground electronic state of the sulfur dioxide molecule (SO2) by fitting novel ab initio energies suitably corrected by scaling its correlation energy. The stationary points of the new surface have been exhaustively analyzed, and the quality of the fit was appreciated from the stratified root-mean-square devia...
On the Rate Constant for the Association Reaction H + CN + Ar → HCN + Ar
Rodrigues, S. P. J.; Varandas, A. J. C.The importance of the chaperon mechanism (via ArCN or ArH complex formation) is investigated for the title reaction. All calculations employ the classical trajectory method to obtain the reactive cross sections while the equilibrium constants are estimated from statistical mechanics. A detailed analysis of the various approximations to the equilibrium constant is presented. Exploratory calculations based on the...
Energy switching potential energy surfaces and spectra of the van der Waals mod...
Varandas, A. J. C.; Rodrigues, S. P. J.; Gomes, P. A. J.We report fully six-dimensional potential surfaces for ArHCN by using the energy switching method. They are valid for all energy regimes and hence suitable for studying the dynamics of a wealth of processes, ranging from the dissociative reaction Ar+HCN --> Ar+H+CN to the rovibrational spectroscopy of the ArHCN van der Waals molecule. Calculations of rovibrational energies with J=0 through J=6 arising from j=0 ...
Dynamics Study of the Reaction Ar + HCN → Ar + H + CN
Rodrigues, S. P. J.; Varandas, A. J. C.A dynamics study of the reaction Ar + HCN → Ar + H + CN for a wide range of initial vibrational and translational energies is reported. All calculations have been carried out with the quasiclassical trajectory method and a realistic potential energy surface for ArHCN. An attempt is made to reproduce the thermal rate coefficient for the reaction. Agreement with experiment is found to be good, and the limitations...
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