Phase Behavior of Ar and Kr Films on Carbon Nanotubes

Kim, Hye Young; Cole, Milton W.; Mbaye, Mamadou; Gatica, Silvina M.

doi:10.1021/jp200410y

Cited by 15 publications

(19 citation statements)

References 40 publications

(43 reference statements)

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“…In wider zigzag NTs (25.83-28.18 Å), Kr forms a low density 1/6 phase. This can be explained observing that, for zigzag NTs (n, 0) with n > 40, the energy of the 1/6 lattice is lower than the energy of the ¼ lattice [26]. The occurrence of the 1/3 and 1/4 phases in narrow NTs is a consequence of the curvature of the surface.…”

Section: Adsorption On a Suspended Carbon Nanotubementioning

confidence: 99%

“…In particular, it is possible to find commensurate lattices of adsorbates. We have done research of commensurate solid phases of Ar and Kr on nanotubes, [26] and there are experimental data for nanotubes [31] and graphite [5]. To search for commensuration we first inspect the E gs versus P at fixed T: a sudden decrease in the gas-surface energy as P increases may indicate a transition to a commensurate phase.…”

Section: Structure and Phase Of The Adsorbed Monolayermentioning

confidence: 99%

“…The chemical potential of the adsorbate is identical to that of the vapor since both are in thermal equilibrium, and the last one is related to the pressure of the vapor through the equation of state. This technique has been extensively used in studies of adsorption in carbon nanotubes and other porous media [22][23][24][25][26].…”

Section: Introduction To Physical Adsorptionmentioning

confidence: 99%

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Adsorption of Gases in Nanomaterials: Theory and Simulations

Mbaye

Maiga

Gatica

2014

Progress in Optical Science and Photonics

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Physical adsorption (physisorption) is the study of atoms or molecules weakly bound to material surfaces. Physisorption-related investigations raise critical questions concerning phase transitions, fractals, wetting transitions, two-dimensional superfluidity, and Van der Waals interactions. This chapter focuses on adsorption of gases (e.g. Ar, Kr, H 2 , CO 2 , and CH 4 ) in nanomaterials, and in particular the authors describe equilibrium properties of the gases adsorbed in carbon nanotubes, graphene and Metal Organic Frameworks (MOFs). The adsorption potential used for developing the theoretical model for studying physisorption involves the summing of two-body interactions, and several important properties of adsorbates can be obtained via simulations, namely equilibrium properties, thermal characteristics, selectivity, wetting features, and structure and phase of the adsorbed monolayer. Applications of physisorption include the separation of cryogenic gases, their storage and their use as a surface characterization tool.

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Section: Adsorption On a Suspended Carbon Nanotubementioning

confidence: 99%

Section: Structure and Phase Of The Adsorbed Monolayermentioning

confidence: 99%

Section: Introduction To Physical Adsorptionmentioning

confidence: 99%

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Adsorption of Gases in Nanomaterials: Theory and Simulations

Mbaye

Maiga

Gatica

2014

Progress in Optical Science and Photonics

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mentioning

confidence: 99%

“…This sensitivity permits investigation of the collective behaviour of 2D matter on a cylinder. Recent simulations have predicted commensuration effects on the phases on the cylindrical nanotube surface 4 , but for simplicity we focus here on argon, which is less likely to exhibit commensurate solid phases.…”

mentioning

confidence: 99%

Surface electron perturbations and the collective behaviour of atoms adsorbed on a cylinder

et al. 2015

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A single-walled carbon nanotube presents a seamless cylindrical graphene surface and is thus an ideal adsorption substrate for investigating the physics of atoms and molecules in two dimensions and approaching the one-dimensional limit [1][2][3][4][5][6][7] . When a suspended nanotube is made into a transistor, frequency shifts of its mechanical resonances allow precise measurement of the adsorbed mass down to the single-atom level [8][9][10] . Here we show that its electrical characteristics are also modified by the adsorbed atoms and molecules, partly as a result of a small charge transfer between them and the carbon surface. We quantify this charge transfer, finding it similar for many di erent species, and use the associated sensitivity of the conductance to carry out the studies of phase transitions, critical scaling, dynamical fluctuations and dissipative metastable states in a system of interacting atoms confined to a cylindrical geometry.Graphite is the substrate of choice for investigating the collective two-dimensional (2D) behaviour of adsorbed atoms and molecules, including transitions between 2D solid (S), liquid (L) and vapour (V) phases 11,12 . In addition, the physical interactions of adsorbates with carbon are important in filters, electrodes, sensors and gas storage, but very little is known experimentally about their effects on the electrons in the surface. Using the unique combination of assets of suspended nanotube transistors, held in equilibrium vapour 6 , we are able to detect the charge transfer from neutral atoms or molecules. Surprisingly, it is of a similar magnitude for all the simple gases tested ( 4 He, Ar, Kr, Xe, N 2 , CO and O 2 ), and although small (much less than predicted [13][14][15] ), at gate voltages near threshold it can produce a large change in conductance. Thus, simply by monitoring the conductance we are able to explore the phase transitions of atoms on a cylinder, seeing 2D critical and triple points and critical behaviour matching the 2D Ising universality class with a finite-size cutoff. We also observe intriguing features in the phase transition dynamics, and discover nonlinear effects of adsorbates interacting with electrical current.Each device, containing a nanotube of diameter ∼2 nm and suspended length ∼1 µm, is mounted in a vapour cell at temperature T and pressure P, the latter being deduced from the pressure P g on an external gauge, as indicated in Fig. 1a (see also Supplementary Information 1). The nanotubes have small bandgaps, producing a minimum in the conductance G near zero gate voltage 16 V g , as can be seen in the characteristics of a device (YB11) shown in Fig. 1b. At lower temperatures, contact barriers cause the nanotube to act as a single-electron transistor exhibiting reproducible Coulomb blockade (CB) oscillations, visible in the characteristic at 4.3 K (blue).Using the arrangement indicated in Fig. 1a, while measuring the conductance we can also detect mechanical resonances and deduce the coverage, φ, which is the number of adsorbates pe...

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A journey toward the heaven of chemical fidelity of intermolecular force fields

James

John

Melekamburath

et al. 2022

WIREs Comput Mol Sci

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Alongside the evolution of density functional theory into a new era led by the dispersion-corrected hybrid density functional theory approaches, formulation of a new generation of intermolecular potentials has also taken the center stage. An ideal potential formulation should desirably possess simplicity of functional forms, physically meaningful parameters, separability of various terms into atomic-level contributions, computational tractability, ability to capture non-additivity of interactions, transferability across different chemical species, and crucially, chemical fidelity in terms of reproducing the benchmark data. The Lennard-Jones potential, one of the popular intermolecular pair potentials for performing large-scale simulations fails to capture the intricate features of molecular interactions. Woven around the central theme of anisotropy in the nature of intermolecular interactions, herein, we describe various landmark contributions in the quest for chemical fidelity of empirical potential formulations that include (i) incorporation of the anisotropic nature of exchange-repulsion and dispersion contributions, (ii) multipolar description of the dispersion terms, (iii) damping functions to provide an accurate description of the asymptotes, and (iv) transferability of intermolecular interaction terms. We illustrate the nuances of intermolecular force field development in the context of modeling the non-covalent interactions governing the (i) binding of atoms and molecules with carbon nanostructures, (ii) molecular aggregates of polycyclic aromatic hydrocarbons, and (iii) interlayer interactions in layered nanostructures. We exemplify the hierarchy of empirical potentials by depicting them on the various rungs of the Jacob's ladder equivalent of density functional theory for the intermolecular force fields. Finally, we discuss some possible futuristic directions in intermolecular force field development.

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Phase Behavior of Ar and Kr Films on Carbon Nanotubes

Cited by 15 publications

References 40 publications

Adsorption of Gases in Nanomaterials: Theory and Simulations

Adsorption of Gases in Nanomaterials: Theory and Simulations

Surface electron perturbations and the collective behaviour of atoms adsorbed on a cylinder

A journey toward the heaven of chemical fidelity of intermolecular force fields

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