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Phys. Rev. B 58, R13426–R13429 (1998)

Heat capacity and vibrational spectra of monolayer films adsorbed in nanotubes

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Ana Maria Vidales*
Department of Physics and Center for Materials Physics, 104 Davey Laboratory, Pennsylvania State University, University Park, Pennsylvania 16802-6300
Laboratorio de Ciencias de Superficies y Medios Porosos-CONICET, Departamento de Física, Universidad Nacional de San Luis, Chacabuco 917, 5700-San Luis, Argentina

Vincent H. Crespi and Milton W. Cole
Department of Physics and Center for Materials Physics, 104 Davey Laboratory, Pennsylvania State University, University Park, Pennsylvania 16802-6300

Received 5 August 1998; published in the issue dated 15 November 1998

Carbon or boron nitride nanotubes can adsorb condensed-phase monolayer films on their inner surfaces. Examples include inert gas or hydrogen films, which form at low temperatures in nanotubes with radius >~5Å. We study the phonon modes and thermodynamic properties of such films. Azimuthal quantization yields quasi-one-dimensional behavior at low temperature, manifested by a heat capacity linear in T, with quasi-two-dimensional behavior at higher temperature; the crossover between these regimes has a universal form, depending only on the ratio of the film radius to the thermal phonon wavelength. The film radius and mean sound speed can be extracted from the temperature dependence of the heat capacity.

© 1998 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevB.58.R13426
DOI:
10.1103/PhysRevB.58.R13426
PACS:
68.60.Dv, 68.15.+e, 68.45.Kg, 61.48.+c

*Present address.

Electronic address:vhc2@psu.edu