Full-dimensional analytical ab initio potential energy surface of the ground state of HOI

Abstract

Effective Hamiltonian for femtosecond vibrational dynamics J. Chem. Phys. 135, 144113 (2011) Analytic energy gradients in combined second order Møller-Plesset perturbation theory and conductorlike polarizable continuum model calculation J. Chem. Phys. 135, 144107 (2011) Extensive ab initio calculations using a complete active space second-order perturbation theory wavefunction, including scalar and spin-orbit relativistic effects with a quadruple-zeta quality basis set were used to construct an analytical potential energy surface (PES) of the ground state of the [H, O, I] system. A total of 5344 points were fit to a three-dimensional function of the internuclear distances, with a global root-mean-square error of 1.26 kcal mol −1 . The resulting PES describes accurately the main features of this system: the HOI and HIO isomers, the transition state between them, and all dissociation asymptotes. After a small adjustment, using a scaling factor on the internal coordinates of HOI, the frequencies calculated in this work agree with the experimental data available within 10 cm −1 .

Thermal Rate Constants for the O(3P) + HBr and O(3P) + DBr Reactions: Transition-State Theory and Quantum Mechanical Calculations

“…Mostly motivated by the absence of high-level theoretical investigations on the title reaction and by our interest in the use of accurate electronic structure calculations to develop PESs for studying atmospherically interesting halogen molecules and reactions, ,,− we computed thermal rate constants for the O( 3 P) + HBr and O( 3 P) + DBr reactions over a wide temperature range and compared the results to the available experimental data. These calculations provide an important test of the PES on which they were made and are based on two different approaches: variational transition-state theory with the small-curvature tunneling correction and quantum reactive scattering calculations with the J -shifting approximation …”

Choice of Optimal Shift Parameter for the Intruder State Removal Techniques in Multireference Perturbation Theory

“…This finding gives us an easily quantified base for determination of an optimal value of the shift parameter to be used in conjunction with each of the available shift techniques. The optimal values of shift parameters determined in this fashion should be more robust than the developed ad hoc values of σ given in MRPT manuals and used every year in numerous MRPT applications, ,− both with respect to the accuracy of the results and with respect to their credibility. Note, however, that the optimal shift parameters are determined in the current study only for bound states of diatomic molecules in conjunction with a single basis set (aug-cc-pVTZ); transferability of these results to other molecular systems as well as to other basis sets yet remains to be established.…”

Estudo teórico da reação O(3P) + HBr: superfícies de energia potencial, cinética e dinâmica

“…Juntamente com outros processos, bromo atômico reativo pode ser gerado pela reação O( 3 P) + HBr −→ OH + Br [14], destruindo uma espécie relativamente inerte, HBr, que é o principal composto envolvido na remoção do bromo da atmosfera [8]. Neste contexto, também estão inseridos um grande número de trabalhos realizados em nosso grupo que investigaram moléculas envolvidas nos ciclos dos halogênios na atmosfera, como a construção da superfície de energia potencial (SEP) para o estado fundamental do sistema HOI/HIO [15], ou compostos análogos, contendo halogênios, enxofre ou selênio: as séries de moléculas diatômicas SCl [16], SBr [17,18], SI [19], SeF [20] e SeCl [21]; as séries de moléculas triatômicas HSCl [22][23][24], HSBr [18,25], HSI [26], HSeF [27] e HSeCl [28]; e as moléculas tetratômicas HSSCl [29], HSSBr [30] e HSSeCl [31].…”