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.

Diffusion dynamics of the li atom on amorphous carbon: A direct molecular orbital-molecular dynamics study.

Abstract: Direct molecular orbital-molecular dynamics (MO-MD) calculation was applied to diffusion processes of the Li atom on a model surface of amorphous carbon and compared with the diffusion mechanism of Li+ ion. A carbon sheet composed of C96H24 was used as the model surface. The total energy and energy gradient on the full dimensional potential energy surface of the LiC96H24 system were calculated at each time step in the trajectory calculation. The optimized structure, where the Li atom is located at the center of mass of the model surface, was used as the initial structure at time zero. Simulation temperatures were chosen in the range of 200-1250 K. The dynamics calculations showed that the Li atom vibrates around the initial position below 250 K, and it moves above 300 K. At middle temperature, the Li atom translates freely on the surface. At higher temperature (1000 K), the Li atom moves from the center to edge region of the model surface and is trapped in the edge. The activation energy calculated for the Li atom is larger than that for the Li+ ion. This difference is due to the fact that the Li atom diffuses together with an unpaired electron on the carbon surface. The diffusion mechanism of the Li atom was discussed on the basis of the theoretical results.

Probing the resonance potential in the F atom reaction with hydrogen deuteride with spectroscopic accuracy.

Abstract: Reaction resonances are transiently trapped quantum states along the reaction coordinate in the transition state region of a chemical reaction that could have profound effects on the dynamics of the reaction. Obtaining an accurate reaction potential that holds these reaction resonance states and eventually modeling quantitatively the reaction resonance dynamics is still a great challenge. Up to now, the only viable way to obtain a resonance potential is through high-level ab initio calculations. Through highly accurate crossed-beam reactive scattering studies on isotope-substituted reactions, the accuracy of the resonance potential could be rigorously tested. Here we report a combined experimental and theoretical study on the resonance-mediated F + HD → HF + D reaction at the full quantum state resolved level, to probe the resonance potential in this benchmark system. The experimental result shows that isotope substitution has a dramatic effect on the resonance picture of this important system. Theoretical analyses suggest that the full-dimensional FH2 ground potential surface, which was believed to be accurate in describing the resonance picture of the F + H2 reaction, is found to be insufficiently accurate in predicting quantitatively the resonance picture for the F + HD → HF + D reaction. We constructed a global potential energy surface by using the CCSD(T) method that could predict the correct resonance peak positions as well as the dynamics for both F + H2 → HF + H and F + HD → HF + D, providing an accurate resonance potential for this benchmark system with spectroscopic accuracy.

Effect of translational and vibrational energy on adsorption: The dynamics of molecular and dissociative chemisorption

Abstract: The dominant features of the molecule–surface potential energy surface which governs the dynamics of molecular and dissociative chemisorption are probed by molecular beam techniques coupled to electron spectroscopy. The collision energy and the vibrational energy of the incident adsorbate are the convenient probes of the interaction potential and high‐resolution electron energy‐loss spectroscopy is the sensitive and chemically specific detector of the result of the dissociative chemisorption event. The dissociative and molecular chemisorption of CH4 and CO on Ni (111) have been studied with these techniques. The results of these studies are summarized to illustrate the power of these techniques to provide information on the mechanism and dynamics of chemisorption.

Sampling along reaction coordinates with the Wang-Landau method

Abstract: The multiple range random walk algorithm recently proposed by Wang and Landau [2001, Phys. Rev. Lett., 86, 2050] is adapted to the computation of free energy profiles for molecular systems along reaction coordinates. More generally, we show how to extract partial averages in various statistical ensembles without invoking simulations with constraints, biasing potentials or unknown parameters. The method is illustrated on a model 10-dimensional potential energy surface, for which analytical results are obtained. It is then applied to the potential of mean force associated with the dihedral angle of the butane molecule in the gas phase and in carbon tetrachloride solvent. Finally, isomerization in a small rocksalt cluster, (NaF)4, is investigated in the microcanonical ensemble, and the results are compared to those of parallel tempering Monte Carlo.

Communication: Highly accurate ozone formation potential and implications for kinetics

Abstract: Atmospheric ozone is formed by the O + O2 exchange reaction followed by collisional stabilization of the O3* intermediate. The dynamics of the O + O2 reaction and to a lesser extent the O3 stabilization depend sensitively on the underlying potential energy surface, particularly in the asymptotic region. Highly accurate Davidson corrected multi-state multi-reference configuration interaction calculations reported here reveal that the minimal energy path for the formation of O3 from O + O2 is a monotonically decaying function of the atom-diatom distance and contains no “reef” feature found in previous ab initio calculations. The absence of a submerged barrier leads to an exchange rate constant with the correct temperature dependence and is in better agreement with experiment, as shown by quantum scattering calculations.