Lennard‐Jones parameters for small diameter carbon nanotubes and water for molecular mechanics simulations from van der Waals density functional calculations

Kaukonen, Maria; Guļāns, Andris; Havu, P.; Kauppinen, Esko I.

doi:10.1002/jcc.22884

Cited by 36 publications

(40 citation statements)

References 51 publications

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“…In addition, our water-carbon interaction is notably anisotropic with δ ≈ 1, unlike most of the previous simulations which assumed an isotropic water-carbon interaction, δ = 0. Similar results (η > 1 kJ/mol, δ > 1 were also found on the basis of vdW-DFT calculations of water outside CNTs [57]. Similar results (η > 1 kJ/mol, δ > 1 were also found on the basis of vdW-DFT calculations of water outside CNTs [57].…”

Section: A Water-carbon Force Fieldsupporting

confidence: 82%

Molecular dynamics simulations of proton-ordered water confined in low-diameter carbon nanotubes

Schmidt

2015

Phys. Chem. Chem. Phys.

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The present work deals with molecular dynamics simulations of water confined in single-walled carbon nanotubes (CNTs), with emphasis on the proton-ordering of water and its polarization. First, the water occupancy of open-ended armchair and zigzag CNTs immersed in water under ambient NPT conditions is calculated for various water models, and for varying Lennard-Jones parameters of the water-carbon interaction. As a function of the CNT diameter, the water density displays several oscillations before converging to the bulk value. Based on these results, the water structures encapsulated in 10 nm long armchair CNTs (n,n) with 5 ≤ n ≤ 10, are investigated under NVT conditions. Inside the smallest nanotubes (n = 5, 6) highly ferroelectric (FE), quasi-one-dimensional water chains are found while inside the other CNTs water molecules assemble into single-walled ice nanotubes (INTs). There are several, near-degenerate minimum energy INT structures: single helical structures were found for 7 ≤ n ≤ 10, in all cases in FE arrangement. In addition, a double helical INT structure was found for n = 8 with an even higher polarization. Prism-like structures were found only for 8 ≤ n ≤ 10 with various FE, ferrielectric (FI), and antiferroelectric (AF, n = 9, 10) proton ordering. The coexistence of the nearly iso-energetic FE, FI, and AF INT structures separated by high barriers renders the molecular dynamics highly metastable, typically with nanosecond timescales at room temperature. Hence, the replica exchange simulation method is used to obtain populations of different INT states at finite temperatures. Many of the FE INT structures confined in low-diameter CNTs are still prevalent at room temperature. Both helix-helix and helix-prism structural transitions are detected which can be either continuous (around 470 K for n = 8) or discontinuous (at 218 K for n = 9). Also melting-like transitions are found in which the INT structures are disrupted leading to a loss of FE or FI ordering of the water orientations. Also these transitions can be either smooth (for n = 7, 8) or abrupt, first-order transitions, at T = 362 K for n = 9 and at T = 285 K for n = 10.

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Section: A Water-carbon Force Fieldsupporting

confidence: 82%

Molecular dynamics simulations of proton-ordered water confined in low-diameter carbon nanotubes

Schmidt

2015

Phys. Chem. Chem. Phys.

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“…Finally, we mention that, in agreement with our previous findings for water interacting with graphene, the overall carbon–water interaction strength obtained from fitting to the current DF‐LCCSD(T) results for water interaction with CNTs is considerably stronger than assumed in most of the previous classical MD simulations, with the exception of the work presented in Refs. [ ] and []. Hence, the present work suggests that the CNTs may be less hydrophobic than commonly anticipated.…”

Section: Discussionmentioning

confidence: 55%

Curvature-dependent adsorption of water inside and outside armchair carbon nanotubes

Lei

Paulus

et al. 2016

J. Comput. Chem.

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The curvature dependence of the physisorption properties of a water molecule inside and outside an armchair carbon nanotube (CNTs) is investigated by an incremental density-fitting local coupled cluster treatment with single and double excitations and perturbative triples (DF-LCCSD(T)) study. Our results show that a water molecule outside and inside (n, n) CNTs (n=4, 5, 6, 7, 8, 10) is stabilized by electron correlation. The adsorption energy of water inside CNTs decreases quickly with the decrease of curvature (increase of radius) and the configuration with the oxygen pointing towards the CNT wall is the most stable one. However, when the water molecule is adsorbed outside the CNT, the adsorption energy varies only slightly with the curvature and the configuration with hydrogens pointing towards the CNT wall is the most stable one. We also use the DF-LCCSD(T) results to parametrize Lennard-Jones (LJ) force fields for the interaction of water both with the inner and outer sides of CNTs and with graphene representing the zero curvature limit. It is not possible to reproduce all DF-LCCSD(T) results for water inside and outside CNTs of different curvature by a single set of LJ parameters, but two sets have to be used instead. Each of the two resulting sets can reproduce three out of four minima of the effective potential curves reasonably well. These LJ models are then used to calculate the water adsorption energies of larger CNTs, approaching the graphene limit, thus bridging the gap between CNTs of increasing radius and flat graphene sheets.

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“…Thus, filling of CNTs with water is favorable from free energy aspects. Up to now, it is recognized that there are many factors affecting the water transport, such as electric fields, pressures, channel shapes . Nonetheless, to the best of our knowledge, the effect of some basic physical parameters on the water transport is still poorly understood, such as the temperature.…”

Section: Introductionmentioning

confidence: 99%

Temperature dependence of the transport of single‐file water molecules through a hydrophobic channel

Yang

2016

J Comput Chem

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Although great effort has been made on the transport properties of water molecules through nanometer channels, our understanding on the effect of some basic parameters are still rather poor. In this article, we use molecular dynamics simulations to study the temperature effect on the transport of single-file water molecules through a hydrophobic channel. Of particular interest is that the water flow and average translocation time both exhibit exponential relations with the temperature. Based on the continuous-time random-walk model and Arrhenius equation, we explore some new physical insights on these exponential behaviors. With the increase of temperature, the water dipoles flip more frequently, since the estimated flipping barrier is less than 2 kB T. Specifically, the flipping frequency also shows an exponential relation with the temperature. Furthermore, the water-water interaction and water occupancy demonstrate linear relations with the temperature, and the water density profiles along the channel axis can be slightly affected by the temperature. These results not only enhance our knowledge about the temperature effect on the single-file water transport, but also have potential implications for the design of controllable nanofluidic machines.

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Lennard‐Jones parameters for small diameter carbon nanotubes and water for molecular mechanics simulations from van der Waals density functional calculations

Cited by 36 publications

References 51 publications

Molecular dynamics simulations of proton-ordered water confined in low-diameter carbon nanotubes

Molecular dynamics simulations of proton-ordered water confined in low-diameter carbon nanotubes

Curvature-dependent adsorption of water inside and outside armchair carbon nanotubes

Temperature dependence of the transport of single‐file water molecules through a hydrophobic channel

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