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Proton dynamics in a single H2O confined in a Buckyball.

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Title: Proton dynamics in a single H2O confined in a Buckyball.
Authors: Nemirovsky, D.1 (AUTHOR), Finkelstein, Y.1,2 (AUTHOR) Finklfam@gmail.com, Moreh, R.3 (AUTHOR)
Source: Vibrational Spectroscopy. Sep2021, Vol. 116, pN.PAG-N.PAG. 1p.
Subjects: Inelastic neutron scattering, Nuclear energy, Vibrational spectra, Frequency spectra, Density functional theory, Hydrogen bonding, Kinetic energy
Abstract: [Display omitted] • The Normal Mode Analysis (NMA) of C- 60 and H 2 O in H 2 O@C 60 has been performed using DFT. • The internal frequencies of isolated H 2 O are altered by less than 1% when inserted into the C 60 fullerene. • The ZPKe(H) of the hydrogen bonds free encapsulated H 2 O assumes a value which resemble that of ice. • In contrast to anomalous Ke(H) values reported by DINS for other H 2 O confining systems, H 2 O@C 60 does not reveal a confinement effect on Ke(H). Using a density functional theory approach with the B3LYP and PBE0 functionals and the 6-G31(d,p) basic set, we simulate the partial vibrational spectra of isolated H 2 O and C 60 molecules, of a periodic H 2 O structure (ice XI) and of a single H 2 O molecule encaged in a buckyball (H 2 O@C 60). A very significant result of the H 2 O@C 60 calculation is that the C-atoms of the hosting fullerene lattice (which for pure C 60 are subjected to a vibrational frequency spectrum that terminates at ∼ 1600 cm−1) were found to participate in the high frequency modes at ∼ 3800 cm−1 of the H 2 O guest, indicating a coupling between the modes of the two sub systems. The effect of temperature between 5 and 300 K on the atomic kinetic energies, Ke(X) (X = C,O,H) were also deduced. The calculated Ke(C) in C 60 using B3LYP was found to be in better agreement with experiment than that of PBE0. Surprisingly, the zero point Ke(H) in the hydrogen bonds (HBs) free H 2 O@C 60 , as well as its T-dependence, were found to be nearly the same as those of the HBs containing condensed bulks of H 2 O, namely ice and liquid water. This result is at variance with that of other H 2 O confining systems measured using deep inelastic neutron scattering, where anomalous Ke(H) values were generically observed. An attempt to understand this behavior is made in view of the observed coupling between the caged H 2 O modes and those of the C 60 host. [ABSTRACT FROM AUTHOR]
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Abstract:[Display omitted] • The Normal Mode Analysis (NMA) of C- 60 and H 2 O in H 2 O@C 60 has been performed using DFT. • The internal frequencies of isolated H 2 O are altered by less than 1% when inserted into the C 60 fullerene. • The ZPKe(H) of the hydrogen bonds free encapsulated H 2 O assumes a value which resemble that of ice. • In contrast to anomalous Ke(H) values reported by DINS for other H 2 O confining systems, H 2 O@C 60 does not reveal a confinement effect on Ke(H). Using a density functional theory approach with the B3LYP and PBE0 functionals and the 6-G31(d,p) basic set, we simulate the partial vibrational spectra of isolated H 2 O and C 60 molecules, of a periodic H 2 O structure (ice XI) and of a single H 2 O molecule encaged in a buckyball (H 2 O@C 60). A very significant result of the H 2 O@C 60 calculation is that the C-atoms of the hosting fullerene lattice (which for pure C 60 are subjected to a vibrational frequency spectrum that terminates at ∼ 1600 cm−1) were found to participate in the high frequency modes at ∼ 3800 cm−1 of the H 2 O guest, indicating a coupling between the modes of the two sub systems. The effect of temperature between 5 and 300 K on the atomic kinetic energies, Ke(X) (X = C,O,H) were also deduced. The calculated Ke(C) in C 60 using B3LYP was found to be in better agreement with experiment than that of PBE0. Surprisingly, the zero point Ke(H) in the hydrogen bonds (HBs) free H 2 O@C 60 , as well as its T-dependence, were found to be nearly the same as those of the HBs containing condensed bulks of H 2 O, namely ice and liquid water. This result is at variance with that of other H 2 O confining systems measured using deep inelastic neutron scattering, where anomalous Ke(H) values were generically observed. An attempt to understand this behavior is made in view of the observed coupling between the caged H 2 O modes and those of the C 60 host. [ABSTRACT FROM AUTHOR]
ISSN:09242031
DOI:10.1016/j.vibspec.2021.103287