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.

Kinetics and Mechanism of the Reactions of Ground-State Y (4d15s2, 2D) with Ethylene and Propylene: Experiment and Theory

Abstract: Bimolecular rate constants, primary products, and kinetic isotope effects for the reactions of Y (4d15s2, 2D) with C2H4 and C2D4 and with C3H6 and C3D6 are measured in a fast flow reactor at 300 K with He/N2 buffer gas at 0.8 Torr. The H2 and D2 elimination products and Y(alkene)-stabilized complexes are detected using single photon ionization at 157 nm and time-of-flight mass spectrometry. We find a small normal isotope effect (kH/kD = 1.75 ± 0.12) for the reaction with ethylene but no significant isotope effect (kH/kD = 1.06 ± 0.07) for the reaction with propylene. We use density functional theory in its B3LYP and mPW1PW91 forms with a large basis set to characterize stationary points on the doublet potential energy surface for the reaction Y + C2H4 → YC2H2 + H2. Theory finds no energy barrier to the formation of a long-range Y−ethylene complex. Subsequent steps involving CH bond insertion by metallacyclopropane complexes are consistent with earlier work. However, a new, low-energy path involves concert...

A simple model for the treatment of imaginary frequencies in chemical reaction rates and molecular liquids.

Abstract: A simple model is presented for treating local imaginary frequencies that are important in the study of quantum effects in chemical reactions and various dynamical processes in molecular liquids. It significantly extends the range of accuracy of conventional local harmonic approximations (LHAs) used in the linearized semiclassical initial value representation/classical Wigner approximation for real time correlation functions. The key idea is realizing that a local Gaussian approximation (LGA) for the momentum distribution (from the Wigner function involving the Boltzmann operator) can be a good approximation even when a LHA for the potential energy surface fails. The model is applied here to two examples where imaginary frequencies play a significant role: the chemical reaction rate for a linear model of the H+H2 reaction and an analogous asymmetric barrier—a case where the imaginary frequency of the barrier dominates the process—and for momentum autocorrelation functions in liquid para-hydrogen at two th...

A combined variational and perturbational study on the vibrational spectrum of P2F4

Abstract: The structure and vibrational spectrum of tetrafluorodiphosphine, P 2 F 4 , were studied by calculating large fractions of the multidimensional potential energy surface at the coupled-cluster level. Vibrational corrections to the geometrical parameters were accounted for by calculating the vibrational wave function using configuration interaction theory (VCI). Fundamental modes, first vibrational overtones and low lying combination bands were computed at the same level and were compared with results from vibrational perturbation theory. A comparison with experimental results is provided.

Ab initio diffusion Monte Carlo calculations of the quantum behavior of CH5+ in full dimensionality

Abstract: We report an ab initio calculation of the potential surface, quantum structures, and zero-point energies of CH5+ and CH2D3+ in full dimensionality. This potential energy surface is a very precise f...

IUPAC critical evaluation of the rotational–vibrational spectra of water vapor. Part IV. Energy levels and transition wavenumbers for D216O, D217O, and D218O

Abstract: This paper is the fourth of a series of papers reporting critically evaluated rotational–vibrational line positions, transition intensities, pressure dependences, and energy levels, with associated critically reviewed assignments and uncertainties, for all the main isotopologues of water. This paper presents energy level and transition data for the following doubly and triply substituted isotopologues of water: D216O, D217O, and D218O. The MARVEL (Measured Active Rotational–Vibrational Energy Levels) procedure is used to determine the levels, the lines, and their self-consistent uncertainties for the spectral regions 0–14 016, 0–7969, and 0–9108 cm−1 for D216O, D217O, and D218O, respectively. For D216O, D217O, and D218O, 53 534, 600, and 12 167 lines are considered, respectively, from spectra recorded in absorption at room temperature and in emission at elevated temperatures. The number of validated energy levels is 12 269, 338, and 3351 for D216O, D217O, and D218O, respectively. The energy levels have been checked against the ones determined, with an average accuracy of about 0.03 cm−1, from variational rovibrational computations employing exact kinetic energy operators and an accurate potential energy surface. Furthermore, the rovibrational labels of the energy levels have been validated by an analysis of the computed wavefunctions using the rigid-rotor decomposition (RRD) scheme. The extensive list of MARVEL lines and levels obtained is deposited in the Supplementary Material of this paper, in a distributed information system applied to water, W@DIS, and on the official MARVEL website, where they can easily be retrieved.