Nature of proton transport in a water-filled carbon nanotube and in liquid water

Chen, Ji; Li, Xinzheng; Zhang, Qianfan; Michaelides, Angelos; Wang, Enge

doi:10.1039/c3cp50218j

Cited by 60 publications

(71 citation statements)

References 57 publications

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“…We anticipate that the routine inclusion of NQEs in ab initio simulations, which is made viable by these techniques, will contribute greatly to our future understanding of aqueous systems, including the solvation of the proton and its mobility in bulk water, in confinement (41,42), and at interfaces.…”

Section: Discussionmentioning

confidence: 99%

Nuclear quantum effects and hydrogen bond fluctuations in water

Ceriotti

Cuny

Parrinello

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

227

260

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The hydrogen bond (HB) is central to our understanding of the properties of water. However, despite intense theoretical and experimental study, it continues to hold some surprises. Here, we show from an analysis of ab initio simulations that take proper account of nuclear quantum effects that the hydrogen-bonded protons in liquid water experience significant excursions in the direction of the acceptor oxygen atoms. This generates a small but nonnegligible fraction of transient autoprotolysis events that are not seen in simulations with classical nuclei. These events are associated with major rearrangements of the electronic density, as revealed by an analysis of the computed Wannier centers and 1 H chemical shifts. We also show that the quantum fluctuations exhibit significant correlations across neighboring HBs, consistent with an ephemeral shuttling of protons along water wires. We end by suggesting possible implications for our understanding of how perturbations (solvated ions, interfaces, and confinement) might affect the HB network in water.path integral molecular dynamics | generalized Langevin equation thermostat | ab initio liquid water D espite its apparent simplicity, liquid water exhibits a number of anomalous properties, such as a decrease in density on freezing, an isobaric density maximum, and its unusually high dielectric constant and heat capacity (1). These, together with its unquestionable importance for climate and life on Earth, have made this substance a subject of intense research by both experiments and simulations.The central concept that has been used to rationalize the peculiar behavior of water is that of the hydrogen bond (HB) (2). The nature of this bond in water has been studied in depth by atomistic computer simulations, which have investigated how it is affected by ionic and electronic polarizability (3, 4), pressure and temperature (5, 6), and nuclear quantum effects (NQEs) (7-9). Furthermore, ab initio molecular dynamics (MD) simulations have been used to shed light on autoionization (10, 11), a process with profound implications for the chemistry of aqueous solutions.In this paper, we investigate the impact of NQEs on the HB in pure water, finding a qualitative increase in fluctuations that leads to a partial dissociation of the covalent O-H bond. The weakening of this covalent bond in the presence of hydrogen bonding is consistent with the red shift of the stretching mode of water upon condensation, as well as with recent experiments demonstrating that selectively exciting the O-H stretch in water leads to a pronounced delocalization of the proton toward the acceptor oxygen atom (12). However, the role of NQEs in governing the extent of this delocalization has not been investigated before now.Our analysis is based on MD simulations of water at different thermodynamic state points, with an ab initio description of the interactions among the nuclei. We also account fully for the quantum nature of the nuclear motion, using a recently developed combination of imaginary time path i...

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Section: Discussionmentioning

confidence: 99%

Nuclear quantum effects and hydrogen bond fluctuations in water

Ceriotti

Cuny

Parrinello

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

227

260

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“…For the solvation of large biomolecules (94,95), small molecules (96)(97)(98), and ions (99) proton transfer by a factor of ~3 (121,122). Experimentally proton diffusion has been observed to 14 be slowed by a factor of ~1.5 upon deuteration (123).…”

Section: Solvation Propertiesmentioning

confidence: 99%

Nuclear Quantum Effects in Water and Aqueous Systems: Experiment, Theory, and Current Challenges

et al. 2016

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Nuclear quantum effects influence the structure and dynamics of hydrogen bonded systems, such as water, which impacts their observed properties with widely varying magnitudes. This review highlights the recent significant developments in the experiment, theory and simulation of nuclear quantum effects in water. Novel experimental techniques, such as deep inelastic neutron scattering, now provide a detailed view of the role of nuclear quantum effects in water's 2 properties. These have been combined with theoretical developments such as the introduction of the competing quantum effects principle that allows the subtle interplay of water's quantum effects and their manifestation in experimental observables to be explained. We discuss how this principle has recently been used to explain the apparent dichotomy in water's isotope effects, which can range from very large to almost nonexistent depending on the property and conditions. We then review the latest major developments in simulation algorithms and theory that have enabled the efficient inclusion of nuclear quantum effects in molecular simulations, permitting their combination with on-the-fly evaluation of the potential energy surface using electronic structure theory. Finally, we identify current challenges and future opportunities in the area.3

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“…Development of a full two-dimensional potential V (r, R) will allow treatment of the secondary geometric isotope effect without introducing the empirical elastic constant K(R) and investigating of the coupling of thermal and quantum fluctuations between R and the X-H stretch. This simple diabatic state model approach can be readily be applied to more complex H-bonded systems such as those associated with solvated Zundel cations [16], excited state proton transfer, double proton transfer in porphycenes [93], and water wires [10]. Finally, we briefly discuss two other future directions.…”

Section: Possible Future Directionsmentioning

confidence: 99%

“…Most of chemistry can be understood in terms of semi-classical motion of nuclei on potential energy surfaces. In contrast, the quantum dynamics of protons involved in hydrogen bonds plays an important role in liquid water [1][2][3], ice [4,5], transport of protons and hydroxide ions in water [6], surface melting of ice [7], the bond orientation of water and isotopic fractionation at the liquid-vapour interface [8], isotopic fractionation in water condensation [9], proton transport in water-filled carbon nanotubes [10], hydrogen chloride hydrates [11], proton sponges [12,13], water-hydroxyl overlayers on metal surfaces [14], and in some proton transfer reactions in enzymes [15]. Experimentally, the magnitude of these nuclear quantum effects are reflected in isotope effects, where hydrogen is replaced with deuterium.…”

Section: Introductionmentioning

confidence: 99%

Effect of quantum nuclear motion on hydrogen bonding

McKenzie

Bekker

Athokpam

et al. 2014

The Journal of Chemical Physics

160

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This work considers how the properties of hydrogen bonded complexes, X-H· · · Y, are modified by the quantum motion of the shared proton. Using a simple two-diabatic state model Hamiltonian, the analysis of the symmetric case, where the donor (X) and acceptor (Y) have the same proton affinity, is carried out. For quantitative comparisons, a parametrization specific to the O-H· · · O complexes is used. The vibrational energy levels of the one-dimensional ground state adiabatic potential of the model are used to make quantitative comparisons with a vast body of condensed phase data, spanning a donor-acceptor separation (R) range of about 2.4 − 3.0Å, i.e., from strong to weak hydrogen bonds. The position of the proton (which determines the X-H bond length) and its longitudinal vibrational frequency, along with the isotope effects in both are described quantitatively. An analysis of the secondary geometric isotope effect, using a simple extension of the two-state model, yields an improved agreement of the predicted variation with R of frequency isotope effects. The role of bending modes is also considered: their quantum effects compete with those of the stretching mode for weak to moderate Hbond strengths. In spite of the economy in the parametrization of the model used, it offers key insights into the defining features of H-bonds, and semi-quantitatively captures several trends.

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Nature of proton transport in a water-filled carbon nanotube and in liquid water

Cited by 60 publications

References 57 publications

Nuclear quantum effects and hydrogen bond fluctuations in water

Nuclear quantum effects and hydrogen bond fluctuations in water

Nuclear Quantum Effects in Water and Aqueous Systems: Experiment, Theory, and Current Challenges

Effect of quantum nuclear motion on hydrogen bonding

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