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.

An ab initio potential surface describing abstraction and exchange for H+CH4.

Abstract: We report an ab initio-based global potential energy surface for H+CH4 that describes the abstraction and exchange reactions. The PES, which is invariant with respect to any permutation of five H atoms, is a fit to 20,728 electronic energies calculated using the partially spin-restricted coupled-cluster method (RCCSD(T)) with a moderately large basis (aug-cc-pVTZ). A first set of quasiclassical trajectory calculations using this PES are reported for the H+CD4-->HD+CD3 reaction at collision energies of 0.65 and 1.52 eV and are compared to experiment and recent direct dynamics calculations done with density functional theory.

Thermal decomposition of silane.

Abstract: The essential features of the potential energy surface for the thermal decomposition of silane have been calculated with extended basis sets, augmented by correlation corrections. It is predicted that the transition state for the molecular elimination lies 56.9 kcal/mol above silane. For the reverse reaction, the transition state is less than 2 kcal/mol above the separated fragments, silylene and molecular hydrogen, but 4.8 kcal/mol above a long-range potential well. In the latter, the silylene-H/sub 2/ separation is 1.78 A, and the bond in H/sub 2/ has stretched by more than 0.05 A. This indicates a significant electronic interaction between the fragments even at the large fragment separation. The depth of the well is less than 1 kcal/mol at the SCF level of theory, but it increases substantially when correlation is introduced into the wave function. Since the calculated SiH bond energy is 22 kcal/mol larger than the activation energy for the molecular elimination, the homolytic cleavage of silane to form silyl radical is not expected to be an important process in the low-energy pyrolysis of silane.

Calibration-quality adiabatic potential energy surfaces for H-3(+) and its isotopologues

Abstract: Calibration-quality ab initio adiabatic potential energy surfaces (PES) have been determined for all isotopologues of the molecular ion H3+. The underlying Born–Oppenheimer electronic structure computations used optimized explicitly correlated shifted Gaussian functions. The surfaces include diagonal Born–Oppenheimer corrections computed from the accurate electronic wave functions. A fit to the 41 655 ab initio points is presented which gives a standard deviation better than 0.1 cm−1 when restricted to the points up to 6000 cm−1 above the first dissociation asymptote. Nuclear motion calculations utilizing this PES, called GLH3P, and an exact kinetic energy operator given in orthogonal internal coordinates are presented. The ro-vibrational transition frequencies for H3+, H2D+, and HD 2+ are compared with high resolution measurements. The most sophisticated and complete procedure employed to compute ro-vibrational energy levels, which makes explicit allowance for the inclusion of non-adiabatic effects, reproduces all the known ro-vibrational levels of the H3+ isotopologues considered to better than 0.2 cm−1. This represents a significant (order-of-magnitude) improvement compared to previous studies of transitions in the visible. Careful treatment of linear geometries is important for high frequency transitions and leads to new assignments for some of the previously observed lines. Prospects for further investigations of non-adiabatic effects in the H3+ isotopologues are discussed. In short, the paper presents (a) an extremely accurate global potential energy surface of H3+ resulting from high accuracy ab initio computations and global fit, (b) very accurate nuclear motion calculations of all available experimental line data up to 16 000 cm−1, and (c) results suggest that we can predict accurately the lines of H3+ towards dissociation and thus facilitate their experimental observation.

A detailed three‐dimensional quantum study of the Li+FH reaction

Abstract: Accurate quantum reactive scattering calculations in the full three‐dimensional physical space have been carried out for the Li+FH reaction at zero total angular momentum using the adiabatically adjusting principal axis of inertia hyperspherical coordinate formalism. The procedures for fitting the potential energy surface, calculating the surface functions, and propagating the solutions in a coupled channel treatment are given and discussed. Features of the resulting reactive probability plots are analyzed, and simple explanations of a number of the quantum resonance and oscillatory features are found.

Potential energy surface for carbon‐dioxide activation by V+: A guided ion beam study

Abstract: A guided ion beam tandem mass spectrometer is used to measure the kinetic energy dependence of the V+(5D) + CO2 reaction and a reverse pathway, VO+(3∑−) + CO. Two intermediates along these reaction pathways, V+(CO2) and OV+(CO), are examined by threshold collision‐induced dissociation experiments with Xe. Thermochemical analyses of the cross sections obtained in these systems allow the measurement of D0(OV+–O) = 3.06±0.40 eV, D0(V+–CO2) = 0.75±0.04 eV, D0(OV+–CO) = 1.05±0.10 eV, and speculative characterization of electronic excitation energies for two states of VO+. Combined with literature information on the electronic states of V+ and VO+, these data enable the potential energy surfaces for this reaction system to be mapped out in some detail. We find that coupling between surfaces of different spin is observed, but that spin conservation plays an important role in both the forward and reverse reactions.