An Improved Variational Calculation of the Lower Vibrational Energy Levels of the Ammonia Molecule

Maessen, Bärbel; Bopp, P.; McLaughlin, Don R.; Wolfsberg, Max

doi:10.1515/zna-1984-1017

Cited by 15 publications

(6 citation statements)

References 5 publications

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“…This value bases on a one-dimensional fit of the double-minimum potential to experimental frequencies and neglects coupling effects from the full NH 3 hypersurface. , A more recent multidimensional treatment derived from experimental rovibrational spectra by Spirko and Kraemer (after correcting for zero-point vibrational effects from complementary modes) 22 and Maessen et al . yields barriers around 1800 cm -1 (ca. 21 kJ mol -1 ), which agree much better with our results.…”

Section: Resultsmentioning

confidence: 99%

Trends in Inversion Barriers IV. The Group 15 Analogous of Pyrrole

et al. 2002

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The inversion process of pyrrole, phosphole, arsole, stibole, and bismole is analyzed in detail by using ab initio and density functional techniques. The results are compared with the corresponding divinyl and diethyl compounds, HM(C2H3)2 and HM(C2H5)2, respectively (M = N, P, As, Sb, and Bi). The inversion barrier increases down the Group 15 elements and from the cyclic, via the divinyl to the diethyl compounds. The inversion process can be rationalized in terms of a second-order Jahn−Teller distortion using HOMO/LUMO energy differences. B3LYP calculations predict that fluorination of the pyrrole ring leads to nonplanar structures of both the tetra- and pentafluoropyrrole.

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Section: Resultsmentioning

confidence: 99%

Trends in Inversion Barriers IV. The Group 15 Analogous of Pyrrole

et al. 2002

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“…Figure 2 shows the profile of energy along this inversion path computed using the surface from Ref. 59 The planar NH 3 geometry that should correspond to the saddle point of the ammonia inversion ͑about 5 kcal mol −1 higher in energy than the pyramidal NH 3 ͒ is predicted by the potential energy surface to be a very stable minimum almost 9 kcal mol −1 below the pyramidal structure. For comparison, we show the inversion path computed using the potential energy surface by Maessen et al.…”

Section: Potential Energy Surfacementioning

confidence: 99%

Seven-dimensional quantum dynamics study of the H+NH3→H2+NH2 reaction

Yang

Corchado

2007

The Journal of Chemical Physics

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Initial state-selected time-dependent wave packet dynamics calculations have been performed for the H+NH3-->H2+NH2 reaction using a seven-dimensional model and an analytical potential energy surface based on the one developed by Corchado and Espinosa-Garcia [J. Chem. Phys. 106, 4013 (1997)]. The model assumes that the two spectator NH bonds are fixed at their equilibrium values. The total reaction probabilities are calculated for the initial ground and seven excited states of NH3 with total angular momentum J=0. The converged cross sections for the reaction are also reported for these initial states. Thermal rate constants are calculated for the temperature range 200-2000 K and compared with transition state theory results and the available experimental data. The study shows that (a) the total reaction probabilities are overall very small, (b) the symmetric and asymmetric NH stretch excitations enhance the reaction significantly and almost all of the excited energy deposited was used to reduce the reaction threshold, (c) the excitation of the umbrella and bending motion have a smaller contribution to the enhancement of reactivity, (d) the main contribution to the thermal rate constants is thought to come from the ground state at low temperatures and from the stretch excited states at high temperatures, and (e) the calculated thermal rate constants are three to ten times smaller than the experimental data and transition state theory results.

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“…A wealth of empirical and theoretical data is available for the inversion barrier associated with the ν 2 umbrella mode in NH 3 1–21. Here, it suffices to say that the best empirical procedures predict effective one‐dimensional, vibrationally averaged barriers in the 2018±10 cm −1 range.…”

Section: Introductionmentioning

confidence: 99%

Equilibrium inversion barrier of NH₃ from extrapolated coupled‐cluster pair energies

et al. 2001

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ABSTRACT:The basis-set convergence of singlet and triplet pair energies of coupled-cluster theory including single and double excitations is accelerated by means of extrapolations based on the distinct convergence behaviors of these pairs. The new extrapolation procedure predicts a nonrelativistic Born-Oppenheimer inversion barrier of 1767 ± 12 cm −1 for NH 3 . An effective one-dimensional, vibrationally averaged barrier of 2021 ± 20 cm −1 is obtained when relativistic effects (+20 cm −1 ), Born-Oppenheimer diagonal corrections (−10 cm −1 ), and zero-point vibrations (+244 cm −1 ) are accounted for.

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An Improved Variational Calculation of the Lower Vibrational Energy Levels of the Ammonia Molecule

Abstract: A new variational calculation of the inversion spectrum of ammonia is reported in which all six vibrational degrees of ammonia are employed. By fitting spectroscopic data, an inversion barrier of 1810 cm"1 is obtained.

Cited by 15 publications

References 5 publications

Trends in Inversion Barriers IV. The Group 15 Analogous of Pyrrole

Trends in Inversion Barriers IV. The Group 15 Analogous of Pyrrole

Seven-dimensional quantum dynamics study of the H+NH3→H2+NH2 reaction

Equilibrium inversion barrier of NH₃ from extrapolated coupled‐cluster pair energies

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An Improved Variational Calculation of the Lower Vibrational Energy Levels of the Ammonia Molecule

Abstract: A new variational calculation of the inversion spectrum of ammonia is reported in which all six vibrational degrees of ammonia are employed. By fitting spectroscopic data, an inversion barrier of 1810 cm"1 is obtained.

Cited by 15 publications

References 5 publications

Trends in Inversion Barriers IV. The Group 15 Analogous of Pyrrole

Trends in Inversion Barriers IV. The Group 15 Analogous of Pyrrole

Seven-dimensional quantum dynamics study of the H+NH3→H2+NH2 reaction

Equilibrium inversion barrier of NH3 from extrapolated coupled‐cluster pair energies

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Equilibrium inversion barrier of NH₃ from extrapolated coupled‐cluster pair energies