Encontrados 75 documentos, a visualizar página 1 de 8
Vibrational energy transfer in N(2D)+N2 collisions: a quasiclassical trajectory...
Galvão, B. R. L.; Varandas, A. J. C.; Braga, J. P.; Belchior, J. C.Rate coefficients for the N(2D)+N2 collisions were calculated employing quasiclassical trajectories and the first available set of potential energy surfaces for such excited nitrogen interactions. The details of the vibrational energy transfer are discussed, such as the contributions from reactive and non-reactive trajectories as well as the contribution of each electronic symmetry. The calculated state-to-stat...
Accurate Double Many-Body Expansion Potential Energy Surface for the Lowest Sin...
Joseph, S.; Varandas, A. J. C.A single-sheeted double many-body expansion potential energy surface is reported for ground-state CH2 by fitting accurate ab initio energies that have been semiempirically corrected by the double many-body-expansion scaled-external-correlation method. The energies of about 2500 geometries have been calculated using the multireference configuration interaction method, with the single diffusely corrected aug-cc-p...
Potential Energy Surface for Ground-State H2S via Scaling of the External Corre...
Song, Y. Z.; Caridade, P. J. S. B.; Varandas, A. J. C.A global double many-body expansion potential energy surface is reported for the electronic ground state of H2S by fitting accurate ab initio energies calculated at the multireference configuration interaction level with the aug-cc-pVQZ basis set, after slightly correcting semiempirically the dynamical correlation by the double many-body expansion-scaled external correlation method. The function so obtained has...
An ab initio study of the interaction between He and C36 with extrapolation to ...
Varandas, A. J. C.http://www.sciencedirect.com/science/article/B6TFN-4SY6W7B-2/1/4f9f0f2a6e06b963255107a7960c33cb
Generalized Uniform Singlet- and Triplet-Pair Extrapolation of the Correlation ...
Varandas, A. J. C.The relationship between the triplet- and singlet-pair interaction coefficients in the uniform singlet- and triplet-pair extrapolation method recently suggested for extrapolating ab initio energies to the one-electron basis set limit is analyzed. Based on the premise that such a ratio is invariant over the configuration space of the molecule, generalizations of the method are investigated and their performance ...
Extrapolating to the One-Electron Basis Set Limit in Polarizability Calculations
Junqueira, G. M. A.; Varandas, A. J. C.We report calculations of polarizabilities using total energies extrapolated to the complete basis set limit. A dual-level scheme has been employed, with the complete basis set limit of the correlation energy determined by the recently reported uniform singlet- and triplet-pair extrapolation method. The finite field approach has been employed, with tensors and averaged polarizabilities for the ground electronic...
A Theoretical Study of Rate Coefficients for the O + NO Vibrational Relaxation
Caridade, P. J. S. B.; Mota, V. C.; Mohallem, J. R.; Varandas, A. J. C.Quasi-classical trajectories have been integrated to study the vibrational relaxation of the O + NO(v) process as a function of the initial vibrational quantum number for T = 298 K, 1500 K, and 3000 K. Two reliable potential energy surfaces have been employed for the A‘ and A‘ ‘ doublet states of NO2. The calculated vibrational relaxation rate constants show a nearly v-independent behavior at room temperature a...
Møller-Plesset perturbation energies and distances for HeC20extrapolated to the...
Varandas, A. J. C.The potential energy surface for the C20-He interaction is extrapolated for three representative cuts to the complete basis set limit using second-order Møller-Plesset perturbation calculations with correlation consistent basis sets up to the doubly augmented variety. The results both with and without counterpoise correction show consistency with each other, supporting that extrapolation without such a correcti...
Dynamics and kinetics of the S + HO2 reaction: A theoretical study
Ballester, M. Y.; Varandas, A. J. C.We report a quasi-classical trajectory study of the S + HO2 reaction using a previously reported global potential energy surface for the ground electronic state of HSO2. Zero-point energy leakage is approximately accounted for by using the vibrational energy quantum mechanical threshold method. Calculations are carried out both for specific ro-vibrational states of the reactants and thermalized ones, with rate ...
Accurate global ab initio potentials at low-cost by correlation scaling and ext...
Varandas, A. J. C.A recently proposed scheme that enables a potential energy surface corresponding to a calculation with a large target basis set to be obtained from small basis set calculations via scaling of the electron correlation at a single-pivotal geometry is generalized to include an arbitrary number of such geometries. If the correlation is extrapolated to the complete basis set limit at the pivotal geometries and used ...
| Financiadores do RCAAP | |||||||
|
|
|
|
|
|
||