A comparative study of structure and electrostatic potential of hydrogen-bonded clusters of neutral ammonia, (NH3)n (n=2–6)

Abu-Awwad, Fakhr M.

doi:10.1016/j.theochem.2004.04.046

Cited by 11 publications

(19 citation statements)

References 27 publications

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“…More interestingly, he pointed out that the functionals B3LYP and B3P86 show high relative stabilities and excellent structural and/or electronic trends in agreement with the MP2 method. By this study, Abu-Awwad 24 confirmed the results of Kulkarni and Pathack 26 for n = 3-6. He also showed that hydrogen bonding energies from B3LYP and B3P86 correlate linearly with the MP2 results with a regression coefficient of 1.00.…”

Section: Introductionsupporting

confidence: 84%

“…Janeiro and Mella 23 used MP2 in conjunction with the aug-cc-pVXZ (X = D, T, Q) basis sets and the Counterpoise procedure, to investigate ammonia clusters from the dimer to the pentamer. They found that the most stable isomer of the tetramer is not a perfect symmetric C 4h as obtained previously, 24,26 but a non-planar cyclic ''boat'' isomer. The same results were confirmed by Yu and Yang 21 using the atom-bond electronegativity equalization method (ABEEM).…”

Section: Introductionsupporting

confidence: 61%

“…Some results, both theoretical and experimental, support the C s conformer 6,7,11,15,16,21,23 while other present the C 2h as the most stable ammonia dimer. 3,4,24 Recently, Gadre et al 25 have pointed out the controversy of the ammonia dimer in a review on molecular clusters.…”

Section: Introductionmentioning

confidence: 99%

“…2,21,23,24,26 Kulkarni and Pathack 26 investigated structures of ammonia clusters from the dimer to the hexamer using the Hartree-Fock (HF) and the second order Møller-Plesset perturbation (MP2) levels of theory with various basis sets; they concluded that from the trimer to the hexamer, the most stable isomers of ammonia clusters were cyclic, while the dimer is an asymmetric C s conformer. Abu-Awwad 24 undertook a comparative study to access the performance of the hybrid density functionals B3P86, B3LYP, B3PW91 and B1LYP, as tools for studying the hydrogen-bond clusters of neutral ammonia clusters (NH 3 ) n=2-6 with a 6-31++G(d,p) basis set. More interestingly, he pointed out that the functionals B3LYP and B3P86 show high relative stabilities and excellent structural and/or electronic trends in agreement with the MP2 method.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Structures and relative stabilities of ammonia clusters at different temperatures: DFT vs. ab initio

Malloum

Fifen

Dhaouadi

et al. 2015

Phys. Chem. Chem. Phys.

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A hydrogen bond network in ammonia clusters plays a key role in understanding the properties of species embedded in ammonia. This network is dictated by the structures of neutral ammonia clusters. In this work, structures of neutral ammonia clusters (NH3)n(=2-10) have been studied at M06-2X/6-31++G(d,p) and MP2/6-31++g(d,p) levels of theory. The analysis of the relative stabilities of various hydrogen bond types has also been studied and vibrational spectroscopy of the ammonia pentamer and decamer is investigated. We noted that M06-2X provides lower electronic energies, greater binding energies and higher structural resolution than MP2. We also noted that at the M06-2X level of theory, the binding energy converges to the experimental vaporization enthalpy faster than that at the MP2 level of theory. As a result, it is found that the M06-2X functional could be more suitable than the MP2 ab initio method in the description of structures and energies of ammonia clusters. However, we found that the electronic energy differences obtained at both levels of computation follow a linear relation with n (number of ammonia molecules in a cluster). As far as the structures of ammonia clusters are concerned, we proposed new "significant" isomers that have not been reported previously. The most remarkable is the global minimum electronic energy structure of the ammonia hexamer, which has an inversion centre and confirms experimental observation. Moreover, we reported the relative stabilities of neutral ammonia clusters for temperatures ranging from 25 to 400 K. The stability of isomers changes with the increase of the temperature. As a result, the branched and less bonded isomers are the most favored at high temperatures and disfavored at low temperatures, while compact and symmetric isomers dominate the population of clusters at low temperatures. In fine, from this work, the global minimum energy structures of ammonia clusters are known for the first time at a given temperature (T ∼ 0-400 K) and at a reliable computational level of theory.

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Section: Introductionsupporting

confidence: 84%

Section: Introductionsupporting

confidence: 61%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Structures and relative stabilities of ammonia clusters at different temperatures: DFT vs. ab initio

Malloum

Fifen

Dhaouadi

et al. 2015

Phys. Chem. Chem. Phys.

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“…The larger ammonia clusters (n > 3) have several nearly degenerate conformations, and interconversions among them are facile. [37][38][39][40][41][42][43][44] Structures of nascent unprotonated cluster cations (NH 3 ) n + have been studied as they are the precursors for further decomposition reactions; that is, vertical ionization energy (VIE) > adiabatic ionization energy (AIE). [32][33][34] (NH 3 ) n + structures are found to have proton transferred type dimer cation cores, NH 4 [45][46][47][48] Protonated cluster ions (NH 3 ) n H + are the main fragment arising from photoionized clusters due to intracluster ion molecule reactions and are the most prominent features in the mass spectrum.…”

Section: Introductionmentioning

confidence: 99%

Dynamics and fragmentation of van der Waals and hydrogen bonded cluster cations: (NH3)n and (NH3BH3)n ionized at 10.51 eV

Yuan

Shin

Bernstein

2016

The Journal of Chemical Physics

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A 118 nm laser is employed as a high energy, single photon (10.51 eV/photon) source for study of the dynamics and fragmentation of the ammonia borane (NH3BH3) cation and its cluster ions through time of flight mass spectrometry. The behavior of ammonia ion and its cluster ions is also investigated under identical conditions in order to explicate the ammonia borane results. Charge distributions, molecular orbitals, and spin densities for (NH3BH3)n and its cations are explored at both the second-order perturbation theory (MP2) and complete active space self-consistent field (CASSCF) theory levels. Initial dissociation mechanisms and potential energy surfaces for ionized NH3BH3, NH3, and their clusters are calculated at the MP2/6-311++G(d,p) level. Protonated clusters (NH3)xH(+) dominate ammonia cluster mass spectra: our calculations show that formation of (NH3)n-1H(+) and NH2 from the nascent (NH3)n(+) has the lowest energy barrier for the system. The only common features for the (NH3)n(+) and (NH3BH3)n(+) mass spectra under these conditions are found to be NHy(+) (y = 0,…,4) at m/z = 14-18. Molecular ions with both (11)B and (10)B isotopes are observed, and therefore, product ions observed for the (NH3BH3)n cluster system derive from (NH3BH3)n clusters themselves, not from the NH3 moiety of NH3BH3 alone. NH3BH2(+) is the most abundant ionization product in the (NH3BH3)n(+) cluster spectra: calculations support that for NH3BH3(+), an H atom is lost from the BH3 moiety with an energy barrier of 0.67 eV. For (NH3BH3)2(+) and (NH3BH3)3(+) clusters, a B(δ+)⋯H(δ-)⋯(δ-)H⋯(δ+)B bond can form in the respective cluster ions, generating a lower energy, more stable ion structure. The first step in the (NH3BH3)n(+) (n = 2, 3) dissociation is the breaking of the B(δ+)⋯H(δ-)⋯(δ-)H⋯(δ+)B moiety, leading to the subsequent release of H2 from the latter cluster ion. The overall reaction mechanisms calculated are best represented and understood employing a CASSCF natural bond orbital description of the valence electron distribution for the various clusters and monomers. Comparison of the present results with those found for solid NH3BH3 suggests that NH3BH3 can be a good hydrogen storage material.

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A review on gold–ammonia bonding patterns

Kryachko

Remacle

2007

Topics in the Theory of Chemical and Physical Systems

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A comparative study of structure and electrostatic potential of hydrogen-bonded clusters of neutral ammonia, (NH3)n (n=2–6)

Cited by 11 publications

References 27 publications

Structures and relative stabilities of ammonia clusters at different temperatures: DFT vs. ab initio

Structures and relative stabilities of ammonia clusters at different temperatures: DFT vs. ab initio

Dynamics and fragmentation of van der Waals and hydrogen bonded cluster cations: (NH3)n and (NH3BH3)n ionized at 10.51 eV

A review on gold–ammonia bonding patterns

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