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.

Intramolecular proton transfer in malonaldehyde: accurate multilayer multi-configurational time-dependent Hartree calculations.

Abstract: Full-dimensional (multilayer) multi-configurational time-dependent Hartree calculations studying the intramolecular proton transfer in malonaldehyde based on a recent potential energy surface (PES) [Wang et al., J. Chem. Phys. 128, 224314 (2008)] are presented. The most accurate calculations yield a ground state tunneling splitting of 23.8 cm(-1) and a zero point energy of 14,678 cm(-1). Extensive convergence tests indicate an error margin of the quantum dynamics calculations for the tunneling splitting of about 0.2 cm(-1). These results are to be compared with the experimental value of the tunneling splitting of 21.58 cm(-1) and results of Monte Carlo calculations of Wang et al. on the same PES which yielded a zero point energy of 14,677.9 cm(-1) with statistical errors of 2-3 cm(-1) and a tunneling splitting of 21.6 cm(-1). The present data includes contributions resulting from the vibrational angular momenta to the tunneling splitting and the zero point energy of 0.2 cm(-1) and 2.4 cm(-1), respectively, which have been computed using a perturbative approach.

Molecular potential energy surfaces by interpolation in Cartesian coordinates

Abstract: We present a new method for expressing a molecular potential energy surface (PES) as an interpolation of local Taylor expansions. By using only Cartesian coordinates for the atomic positions, this method avoids redundancy problems associated with the use of internal coordinates. The correct translation, rotation, inversion, and permutation invariance are incorporated in the PES via the interpolation method itself. The method is most readily employed for bound molecules or clusters and is demonstrated by application to the vibrational motion of acetylene.

Mode selectivity for a "central" barrier reaction: Eight-dimensional quantum studies of the O(3P) + CH4 → OH + CH3 reaction on an ab initio potential energy surface

Abstract: The dynamics of a combustion reaction, namely, O(P-3) + CH4 -> OH + CH3, is investigated with an eight-dimensional quantum model that includes representatives of all vibrational modes of CH4 and with a full-dimensional quasi-classical trajectory (QCT) method. The calculated excitation functions for the ground vibrational state CH4 agree well with experiment. Both quantum and QCT results suggest that excitation of the stretching modes of CH4 enhances the reaction, while the bending and umbrella modes have a smaller impact on reactivity, again consistent with experimental findings. However, none of the vibrational excitations has comparable efficiency in promoting the reaction as translational energy.

The F+HD --> DF(HF)+H(D) reaction revisited: Quasiclassical trajectory study on an ab initio potential energy surface and comparison with molecular beam experiments

Abstract: The dynamics of the F+HD reaction has been studied by means of quasiclassical trajectory calculations on an ab initio potential energy surface (PES) at several collision energies At the collision energy of 859 meV and for the DF+H isotopic channel of the reaction, there is a remarkable agreement between calculated and experimental results, in both the center of mass (cm) differential cross sections (DCS) and in the simulation of the laboratory (LAB) time of flight (TOF) and angular distributions (AD) The good agreement also extends to the lower collision energy of 586 meV for this channel of the reaction In contrast, the simulation of the LAB angular distributions for the HF+D channel shows strong discrepancies between theory and experiment at both collision energies, which can be traced back to the absence of a forward peak in the calculated cm DCS for HF(v’=3) Simulations made from QCT calculations on other PES with important HF(v’=3) forward scattering contributions also fail to reproduce the

Effect of curvature of the reaction path on dynamic effects in endothermic chemical reactions and product energies in exothermic reactions

Abstract: Collinear quasiclassical trajectories are examined for two realistic potential energy surfaces for atom−diatomic molecule reactions for two reaction attributes: (1) vibrational energy of the products of a thermal−energy exothermic reaction; (2) threshold energy for endothermic reaction of ground−state reagents. Eight different mass combinations are studied. The potential energy surfaces differ primarily in the amount of potential energy released in an exothermic reaction before and in the region of large curvature of the minimum−energy path and in the curvature of the repulsive potential energy contours when all three atoms are close. For attribute (1), we find the results are qualitatively correlated by the theory of Hofacker and Levine although, contrary to previous work, one potential energy surface shows high mixed energy release (in the language of Polanyi and co−workers) but low excitation to product vibration for five different mass combinations. For reaction attribute (2), we find one surface has a high translational threshold (or no reaction at any energy) for six mass combinations, while the other surface shows this behavior in only three cases. Thus, this type of surface provides an exception to previous generalizations that extra vibrational energy is required for very endothermic reactions with late barriers. This demonstrates the importance of the location of the curvature of the reaction channel for such reaction attributes. Very accurate determinations of potential energy surfaces will be required to make reliable predictions of reaction attributes such as (1) and (2) for real systems. Analysis of the details of the trajectories shows that the high threshold can generally be attributed to reflection before the saddle point of the surface rather than to recrossing the saddle point region. The vibrational excitation of reagents in nonreactive collisions is also strongly effected by curvature of the minimum−energy path.