title: Influence of longitudinal isotope substitution on the thermal conductivity of carbon nanotubes: results of nonequilibrium molecular dynamics and local density functional calculations.
abstract: We report reverse nonequilibrium molecular dynamics calculations of the thermal conductivity of isotope substituted (10,10) carbon nanotubes (CNTs) at 300 K. (12)C and (14)C isotopes both at 50% content were arranged either randomly, in bands running parallel to the main axis of the CNTs or in bands perpendicular to this axis. It is found that the systems with randomly distributed isotopes yield significantly reduced thermal conductivity. In contrast, the systems where the isotopes are organized in patterns parallel to the CNTs axis feature no reduction in thermal conductivity when compared with the pure (14)C system. Moreover, a reduction of approximately 30% is observed in the system with the bands of isotopes running perpendicular to the CNT axis. The computation of phonon dispersion curves in the local density approximation and classical densities of vibrational states reveal that the phonon structure of carbon nanotubes is conserved in the isotope substituted systems with the ordered patterns, yielding high thermal conductivities in spite of the mass heterogeneity. In order to complement our conclusions on the (12)C-(14)C mixtures, we computed the thermal conductivity of systems where the (14)C isotope was turned into pseudo-atoms of 20 and 40 atomic mass units.
authors.affiliation: Eduard-Zintl-Institut für Anorganische und Physikalische Chemie, Technische Universität Darmstadt, D-64287 Darmstadt, Germany.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Leroy
authors.affiliation: Bruker Biospin GmbH, Silberstreifen, D-76287 Rheinstetten, Germany.
authors.forename: Joachim
authors.initials: J
authors.lastname: Schulte
authors.affiliation: Department of Mechanical Engineering, Iowa State University, Ames, Iowa 50011, USA.
authors.forename: Ganesh
authors.initials: G
authors.lastname: Balasubramanian
authors.affiliation: Eduard-Zintl-Institut für Anorganische und Physikalische Chemie, Technische Universität Darmstadt, D-64287 Darmstadt, Germany.
authors.forename: Michael C
authors.initials: MC
authors.lastname: Böhm