Microsolvation of lithium in ammonia: Dissociation energies and spectroscopic parameters of small clusters (n=1 and 2) and their cations

Salter, Tom E.; Ellis, Andrew M.

doi:10.1016/j.chemphys.2006.11.038

Cited by 8 publications

(25 citation statements)

References 23 publications

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“…Conformer 1b possesses D 3d symmetry, with the two NH 3 molecules in staggered orientation, and is the global minimum conformer for both Li + and Na + , in accord with previous ab initio results. 21,24 A previously reported linear structure in which the two ammonia molecules are in eclipsed orientation 28 (D 3 symmetry, not shown in Figure 1) corresponds to a transition state. Conformer 1c is a bent, C s -symmetric structure and represents the global minimum energy for K + , Rb + , and Cs + (see Table 1).…”

Section: Journal Of Chemical Theory and Computationmentioning

confidence: 91%

Molecular Dynamics Investigation of Alkali Metal Ions in Liquid and Aqueous Ammonia

Orabi

Lamoureux

2013

J. Chem. Theory Comput.

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A polarizable potential model for M(+)-NH3 interactions (M(+) = Li(+), Na(+), K(+), Rb(+), Cs(+)) is optimized based on the ab initio properties of the ion-ammonia dimers calculated at the MP2 level of theory. The optimized model reproduces the ab initio binding energies of M(+)(NH3)n (n = 2-4) and M(+)(NH3)n(H2O)m (n, m = 1-3 and n + m ≤ 4) clusters and gives relative solvation free energies in liquid ammonia in good agreement with experimental data, without further adjustments. It also reproduces binding cooperativity in ion-ammonia and ion-ammonia-water clusters. The model is used in molecular dynamics simulations of isolated ions in liquid ammonia and in aqueous ammonia solutions with various ammonia molar fractions (0.0 ≤ xNH3 ≤ 1.0). Simulations in liquid ammonia show coordination numbers of 4.0 for Li(+), 5.3 for Na(+), 6.1 for K(+), 6.7 for Rb(+), and 7.7 for Cs(+), in very good agreement with available experimental results. Simulations of ions in aqueous ammonia show preferential solvation by water in their first solvation shells and preferential solvation by ammonia in their second shells. Potentials of mean force are calculated between each ion and NH3 in liquid water, and between each ion and H2O in liquid ammonia. The results suggest that, in liquid water, Li(+) and Na(+) bind NH3 in their second solvation shells only, while Cs(+) binds NH3 in its first solvation shell only (K(+) and Rb(+) ions show only weak affinity for NH3 in water). In liquid ammonia, the ions bind H2O in their first solvation shells with an affinity following the trend Li(+) > Na(+) > K(+) ≈ Rb(+) > Cs(+).

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Section: Journal Of Chemical Theory and Computationmentioning

confidence: 91%

Molecular Dynamics Investigation of Alkali Metal Ions in Liquid and Aqueous Ammonia

Orabi

Lamoureux

2013

J. Chem. Theory Comput.

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“…This ranges between 24 and 28 kJ mol À1 NH 3 , a value signicantly lower than the binding energy of Li-NH 3 clusters reported in the literature (see also discussion below). 36…”

Section: Ex-situ Nh 3 Desorptionmentioning

confidence: 99%

Ammonia-storage in lithium intercalated fullerides

et al. 2015

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“…The DFT value shown in Table II is probably unreasonably high, and, thus, more weight is given here to the MP2 value, since MP2 calculations are known to yield more reliable estimates of alkali-solvent dissociation energies than DFT calculations. 15 As mentioned earlier, a considerable error margin is expected for the dissociation energy given the level of approximations involved, and so, the 3 + 0 isomer cannot be ruled out on the basis of these dissociation energy calculations. Nevertheless, it is worth noting that the energy required to remove a methylamine molecule from the 2 + 1 cluster will be much lower than that of the 3 + 0 isomer on account of the weakly bound solvent molecule held in the outer shell for the former isomer.…”

Section: Li"nh 2 Ch 3 …mentioning

confidence: 99%

“…The lowest energy isomer is the 2 + 0 species, which adopts a strongly bent N-Li-N framework reminiscent of the bent global minimum structure found for the Li͑NH 3 ͒ 2 cluster. 15 Interestingly, the N-Li-N-C dihedral angle lies close to planarity in a configuration that brings the methyl groups into close prox-imity. Calculations carried out for starting geometries with the methyl groups more remote from each other, in order to minimize steric repulsion, either did not converge or reverted back to the minimum energy isomer.…”

Section: Linh 2 Ch 3 and Li"nh 2 Ch 3 …mentioning

confidence: 99%

Coordination structures of lithium-methylamine clusters from infrared spectroscopy and ab initio calculations

Salter

Ellis

2007

The Journal of Chemical Physics

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Spectra of clusters formed between lithium atoms and methylamine molecules are reported for the first time. Mass-selective infrared spectra of Li͑NH 2 CH 3 ͒ n have been recorded in both the N-H and C-H stretching fundamental regions. The infrared spectra are broadly in agreement with ab initio predictions, showing redshifted N-H stretching bands relative to free methylamine and a strong enhancement of the N-H stretching fundamentals relative to the C-H stretching fundamentals. The ab initio calculations suggest that, for n = 3, the methylamine molecules bunch together on one side of the lithium atom to minimize repulsive interactions with the unpaired electron density. The addition of a fourth methylamine molecule results in closure of the inner solvation shell and, thus, Li͑NH 2 CH 3 ͒ 5 is forced to adopt a two-shell coordination structure. This is consistent with neutron diffraction studies of concentrated lithium/methylamine solutions, which also suggest that the first solvation shell around the lithium atom can contain a maximum of four methylamine molecules.

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Microsolvation of lithium in ammonia: Dissociation energies and spectroscopic parameters of small clusters (n=1 and 2) and their cations

Cited by 8 publications

References 23 publications

Molecular Dynamics Investigation of Alkali Metal Ions in Liquid and Aqueous Ammonia

Molecular Dynamics Investigation of Alkali Metal Ions in Liquid and Aqueous Ammonia

Ammonia-storage in lithium intercalated fullerides

Coordination structures of lithium-methylamine clusters from infrared spectroscopy and ab initio calculations

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