Potential energy surface

About: Potential energy surface is a research topic. Over the lifetime, 11674 publications have been published within this topic receiving 307691 citations.

Rotational effects in the H2+OH→H+H2O reaction rate: Full-dimensional close-coupling results

Abstract: The dependence of the thermal rate constant of the H2+OH→H+H2O reaction on the rotational motion is investigated. Full-dimensional quantum calculations accurately accounting for the overall rotation, i.e., close-coupling (CC) calculations, are presented. These calculations are based on a flux correlation function approach and employ a rigorously correct statistical sampling scheme for the rotational degrees of freedom and the multi-configurational time-dependent Hartree (MCTDH) approach for the wavefunction propagation. They provide a first strictly correct description of the rate constant of the title reaction on the Schatz–Elgersma potential energy surface. The results are compared to approximate results obtained within the centrifugal sudden or coupled states (CS) approximation and the J-shifting approximation. No significant differences have been found between the accurate results and rate constants obtained within the CS approximation. In contrast, the J-shifting approximation overestimates the accur...

A quantum mechanical study on the formation of PCDD/Fs from 2-chlorophenol as precursor.

Abstract: The most direct route to the formation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in combustion and thermal processes is the gas-phase reaction of chemical precursors such as chlorinated phenols. Detailed insight into the mechanism and kinetics properties is a prerequisite for understanding the formation of PCDD/Fs. In this paper, we carried out molecular orbital theory calculations for the homogeneous gas-phase formation of PCDD/Fs from 2-chlorophenol (2-CP). The profiles of the potential energy surface were constructed, and the possible formation pathways are discussed. The single-point energy calculation was carried out at the MPWB1K/6−311+G(3f,2p) level. Several energetically favorable formation pathways were revealed for the first time. The rate constants of crucial elementary steps were deduced over a wide temperature range of 600∼1200 K using canonical variational transition-state theory (CVT) with small curvature tunneling contribution (SCT). The rate-temperature formulas wer...

The reaction of n- and i-C4H5 radicals with acetylene.

Abstract: In this article, we discuss the reactions of i-C4H5 and n-C4H5 with acetylene. Both have been proposed as possible cyclization steps, forming benzene or fulvene, in rich flames burning aliphatic fuels. The relevant parts of the potential energy surface were determined from rQCISD(T) calculations extrapolated to the infinite-basis-set limit. Using this information in a Rice−Ramsperger−Kassel−Marcus-based master equation, we have calculated thermal rate coefficients and product distributions for both reactions as a function of temperature and pressure. The results are cast in forms that can be used in modeling, and the implications of the results for flame chemistry are discussed.

"Roaming" dynamics in CH3CHO photodissociation revealed on a global potential energy surface.

Abstract: We present a quasiclassical trajectory study of the photodissociation of CH3CHO to molecular and radical products, CH4 + CO and CH3 + HCO, respectively, using global ab initio-based potentials energy surfaces. The molecular products have a well-defined potential barrier transition state (TS) but the dynamics exhibit strong deviations from the TS pathway to these products. The radical products are formed via a variational TS. Calculations are reported at total energies corresponding to photolysis wavelengths of 308, 282, 264, 248 and 233 nm. The results at 308 nm focus on a comparison with experiment [Houston, P. L.; Kable, S. H. Proc. Natl. Acad. Sci. U.S.A. 2006, 103, 16079] and the elucidation of the nature and extent of non-TS reaction dynamics to form the molecular products, CH4 + CO. At the other wavelengths the focus is the branching ratio of these products and the radical products, CH3 + HCO.