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

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

doi:10.1515/zna-1982-0417

Cited by 12 publications

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“…Therefore, in agreement with simulation re sults discussed below, there is no strong preference for a hydrogen bond along the lone pair direction. How ever, the distance where the minimum occurs changes considerably.Several intramolecular potential surfaces for the ammonia molecule are given in the literature [13][14][15], They are all based on spectroscopic data. In this study we decided to use the surface by Spirko [14], which accounts for the inversion mode of the molecule by means of a strongly anharmonic potential.…”

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confidence: 99%

Molecular Dynamics Study of a Lithium Ion in Ammonia

Hannongbua

Ishida

Spohr

et al. 1988

Zeitschrift Für Naturforschung A

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A Molecular Dynamics simulation of a solution of one Li+ in 215 NH3 molecules has been performed at an average temperature of 235 K. A newly developed flexible model for NH3 is employed and the Li + -NH3 interactions are derived from ab initio calculations. The structure of the solution is described by radial distribution functions and the orientation of the molecules. A solvation number of six is found for Li+ and a strong preference of the solvation shell molecules exists for an orientation where the Li + -N vector and the dipole moment direction of NH3 are parallel. The self-diffusion coefficient, the hindered translational motions and librations are calcula ted separately for the ammonia molecules in the solvation shell and in the bulk. The effect of Li + on intramolecular geometry and vibrations is reported. The physics of metal solutions in liquid ammonia is an interesting topic in modern physical chemistry. For example, striking differences between solvation of metal atoms in water and liquid ammonia exist. Diss olving alkali metal atoms in water leads to oxidation to the monovalent cations, the formation of hydroxide ions, and H2 evolution. On the contrary, in liquid ammonia free electrons exist if the alkali metal con centration exceeds a few mole percent [1], The electri cal conductivity of a 20 mole percent lithium solution is higher than that of liquid mercury at room tempera ture [2], Structural information about bulk ammonia as well as metal ion and electron solvation is necessary in order to understand the properties of these solutions. The only X-ray scattering experiment on liquid am monia reported so far has been performed by Narten [3]. Only the nitrogen-nitrogen radial distribution function (RDF) can be extracted reliably from these data. The available neutron scattering data [4] are not analysed in terms of atom-atom RDFs. Neutron scat tering experiments with isotopic substitution, which yield information also about the nitrogen-hydrogen and hydrogen-hydrogen RDFs, have not been per formed. Considerable efforts have been made in attempts to overcome this lack of experimental information on liquid ammonia by means of computer simulations [5][6][7][8][9], which yield information about all three atomatom RDFs. Recently, the electron solvation in liquid ammonia has been treated by the quantum path inte gral Monte Carlo method on the basis of a pseudopotential ansatz for the electron ammonia interactions [10].In this work, the structure of the solvation shell of a lithium ion dissolved in NH3 will be discussed in detail and compared with some preliminary results from a neutron diffraction experiment [4] and a recent Molecular Dynamics (MD) simulation [11]. In addi tion, the dynamical properties of ammonia in the bulk and in the solvation shell of the ion have been calcu lated separately from the simulation and are com pared with experimental data. The flexibility of the ammonia model employed permits the investigation of the effect of Li+ on the intramolecular vibrations of NH3 and the comparison...

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confidence: 99%

Molecular Dynamics Study of a Lithium Ion in Ammonia

Hannongbua

Ishida

Spohr

et al. 1988

Zeitschrift Für Naturforschung A

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“…B. C parameter set to yield better agreement with the inversion spectrum while keeping Vr % as in [1], This new parameter set was found.…”

Section: Resultsmentioning

confidence: 94%

“…As in [1], the inversion potential has the form V " = A92 + Bex p (~Cd2) 0340-4811 / 84 / 1000-1009 $ 01.30/0. -Please order a reprint rather than making your own copy.…”

Section: Resultsmentioning

confidence: 99%

“…The Whitehead-Handy procedure as applied to ammonia has already been described in the previous publication [1], The basis functions are products of six harmonic oscillator wavefunctions corresponding to the six normal frequencies of a "planar ammonia" molecule. The frequency param eters of the harmonic oscillator wavefunctions may be considered as variational parameters.…”

Section: Methodsmentioning

confidence: 99%

“…A full variational calculation of the lower vibrational energy levels (J = 0) of ammonia has been recently re ported [1]. All six internal degrees of freedom of the molecule were employed.…”

Section: Introductionmentioning

confidence: 99%

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

Maessen

Bopp

McLaughlin

et al. 1984

Zeitschrift Für Naturforschung A

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Variational calculations on ammonia using two symmetrical normal modes

Huang

Wolfsberg

1991

Int. J. Quantum Chem.

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Variational calculations have been camed out on the ammonia molecule using two-dimensional potential energy functions. The two dimensions used are the inversion and symmetrical stretching coordinates. Ifthe potential function includes a term to describe the interaction between these two coordinates, the results are as good as those obtained in other studies using a six-dimensional potential function. The barrier height for the new potential function is 1857.5 cm-'.

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

Cited by 12 publications

References 0 publications

Molecular Dynamics Study of a Lithium Ion in Ammonia

Molecular Dynamics Study of a Lithium Ion in Ammonia

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

Variational calculations on ammonia using two symmetrical normal modes

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