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.

Six-dimensional quantum calculations of highly excited vibrational energy levels of hydrogen peroxide and its deuterated isotopomers

Abstract: We report accurate calculations of vibrational energy levels of HOOH, DOOD, and HOOD up to 10 000 cm−1 above the zero-point energy levels on a high-quality ab initio potential energy surface. These energies were determined by the Lanczos algorithm based on repetitive matrix-vector multiplication. The six-dimensional vibrational Hamiltonian in the diatom–diatom Jacobi coordinate system was discretized in a mixed basis/grid representation. A direct product potential optimized discrete variable representation was used for the radial coordinates, while nondirect product spherical harmonics were employed for the angular degrees of freedom. The calculation and storage of the potential matrix in the angular finite basis representation were avoided by using a series of one-dimensional pseudo-spectral transformations to a direct product angular coordinate grid. The diatom–diatom exchange symmetry, when applicable, was incorporated into the basis, which significantly enhanced the efficiency for symmetric isotopomer...

Classical Trajectory Analysis of the Reaction F+H2→HF+H

Abstract: A classical trajectory analysis has been made for the reaction F+H2→HF+H using a semiempirical potential energy surface. The reaction cross sections, energy distributions among reaction products, and angular distributions of products were determined as functions of initial relative velocity for low‐lying rotation–vibration states of H2 from Monte Carlo averages over a large number of trajectories. The modified London–Eyring–Polanyi–Sato surface used is characterized by a 1.68 kcal barrier in the entry valley with a net drop of 31.3 kcal to the exit valley occurring with F approaching H2. The reaction cross sections for H2 with υ = 0, J = 1 increased with relative velocity from a threshold value at a translational energy of 2.1 kcal to ∼ 6 A2 at 14 kcal. Rotational energy had little effect on the cross sections. For υ = 1, J = 1 the translational energy threshold was slightly lower and the upper limit to cross sections was ∼ 8 A2. The HF product was found to be strongly excited vibrationally with an averag...

Graphite-diamond phase coexistence study employing a neural-network mapping of the ab initio potential energy surface

Abstract: An interatomic potential for the diamond and graphite phases of carbon has been created using a neural-network (NN) representation of the ab initio potential energy surface. The NN potential combines the accuracy of a first-principles description of both phases with the efficiency of empirical force fields and allows one to perform a molecular-dynamics study, of ab initio quality, of the thermodynamics of graphite-diamond coexistence. Good agreement between the experimental and calculated coexistence curves is achieved if nuclear quantum effects are included in the simulation.

State-to-State Rates for the D + H2(v = 1, j = 1) → HD(v', j') + H Reaction: Predictions and Measurements

Abstract: A fully quantal wavepacket approach to reactive scattering in which the best available H3 potential energy surface was used enabled a comparison with experimentally determined rates for the D + H2(v = 1, j = 1) → HD(v9 = 0, 1, 2; j9) + H reaction at significantly higher total energies (1.4 to 2.25 electron volts) than previously possible. The theoretical results are obtained over a sufficient range of conditions that a detailed simulation of the experiment was possible, thus making this a definitive comparison of experiment and theory. Good to excellent agreement is found for the vibrational branching ratios and for the rotational distributions within each product vibrational level. However, the calculated rotational distributions are slightly hotter than the experimentally measured ones. This small discrepancy is more marked for products for which a larger fraction of the total energy appears in translation. The most likely explanation for this behavior is that refinements are needed in the potential energy surface.

Direct Dynamics Method for the Calculation of Reaction Rates

Abstract: Accurate quantum dynamics calculations for atom-diatom reactions have advanced to the stage where the nuclear-motion Schrodinger equation can be solved essentially exactly for a given potential energy surface [ 1]. For example, we recently reported accurate quantum mechanical rate constants for the reaction D + H2 → HD + H over a wide temperature range [2]. In this case the potential energy surface is very well known, and the dynamical results for the most accurate potential energy surface [3] agree with experiment [4] within 12% (maximum deviation) over the 200-900K temperature interval, with slightly large errors at higher T (16% at 1300 K, 22% at 1500 K). This is quite satisfying for a totally ab initio calculation of a chemical reaction rate.