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.

“Direct” and “Correct” Calculation of Canonical and Microcanonical Rate Constants for Chemical Reactions

Abstract: Theoretical approaches for calculating rate constants of chemical reactionseither the microcanonical rate for a given total energy k(E) or the canonical rate for a given temperature k(T)are described that are both “direct”, i.e., bypass the necessity of having to solve the complete state-to-state quantum reactive scattering problem, yet also “correct”, i.e., in principle exact (given a potential energy surface, assuming nonrelativistic quantum mechanics, etc.) Applications to a variety of reactions are presented to illustrate the methodology for various dynamical situations, e.g., transition-state-theory-like dynamics where the system moves directly through the interaction (transition-state) region and reactions that form long-lived collision complexes. It is also shown how this rigorous quantum theory can be combined with the Lindemann mechanism for describing the effects of collisions with a bath gas, so as to be able to treat recombination reactions and other effects of pressure. Finally, several ways ...

The vibrational energies of ozone up to the dissociation threshold: Dynamics calculations on an accurate potential energy surface

Abstract: We present an ab initio potential energy surface for the ground electronic state of ozone. It is global, i.e., it covers the three identical C2v (open) minima, the D3h (ring) minimum, as well as the O(3P)+O2(3Σg−) dissociation threshold. The electronic structure calculations are performed at the multireference configuration interaction level with complete active space self-consistent-field reference functions and correlation consistent polarized quadruple zeta atomic basis functions. Two of the O–O bond distances, R1 and R2, and the O–O–O bending angle are varied on a regular grid (ca. 5000 points with R1⩾R2). An analytical representation is obtained by a three-dimensional cubic spline. The calculated potential energy surface has a tiny dissociation barrier and a shallow van der Waals minimum in the exit channel. The ring minimum is separated from the three open minima by a high potential barrier and therefore presumably does not influence the low-temperature kinetics. The dissociation energy is reproduce...

Nonadiabatic dynamics at metal surfaces: Independent-electron surface hopping

Abstract: Recent experiments have shown convincing evidence for nonadiabatic energy transfer from adsorbate degrees of freedom to surface electrons during the interaction of molecules with metal surfaces. In this paper, we propose an independent-electron surface hopping algorithm for the simulation of nonadiabatic gas-surface dynamics. The transfer of energy to electron-hole pair excitations of the metal is successfully captured by hops between electronic adiabats. The algorithm is able to account for the creation of multiple electron-hole pairs in the metal due to nonadiabatic transitions. Detailed simulations of the vibrational relaxation of nitric oxide on a gold surface, employing a multistate potential energy surface fit to density functional theory calculations, confirm that our algorithm can capture the underlying physics of the inelastic scattering process.

Revised Anisotropic Site Potentials for the Water Dimer and Calculated Properties

Abstract: Two new parametrizations of a recent ab initio polarizable anisotropic site potential for water are presented. The new versions improve the description of the electrostatic interactions, add an explicit charge-transfer term, and use more accurate dispersion coefficients from the recent literature. To assess the merits of the new models, the potential energy surface of the dimer is analyzed and a comparison is made with 12 other polarizable potentials for water in the literature, most of them being currently used in computer simulation. The structure, energy, and harmonic intermolecular frequencies of the stationary points have been determined and compared with the best available ab initio calculations. The energy barriers and pathways for hydrogen atom interchange within the dimer are discussed. The second virial coefficient B(T) of steam between 373 and 973 K, including first-order quantum corrections, is reported. For all the models, the quantum corrections are found to be significant at the lowest temp...

Vibrationally promoted dissociation of water on Ni(111).

Abstract: Water dissociation on transition-metal catalysts is an important step in steam reforming and the water-gas shift reaction. To probe the effect of translational and vibrational activation on this important heterogeneous reaction, we performed state-resolved gas/surface reactivity measurements for the dissociative chemisorption of D2O on Ni(111), using molecular beam techniques. The reaction occurs via a direct pathway, because both the translational and vibrational energies promote the dissociation. The experimentally measured initial sticking probabilities were used to calibrate a first-principles potential energy surface based on density functional theory. Quantum dynamical calculations on the scaled potential energy surface reproduced the experimental results semiquantitatively. The larger increase of the dissociation probability by vibrational excitation than by translation per unit of energy is consistent with a late barrier along the O-D stretch reaction coordinate.