THE DISPARATE THERMAL CONDUCTIVITY OF CARBON

THE DISPARATE THERMAL CONDUCTIVITY OF CARBON - MTE 8(1)...

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Unformatted text preview: MTE 8(1) #14664 Microscale Thermophysical Engineering, 8:61–69, 2004 Copyright © Taylor & Francis Inc. ISSN: 1089-3954 print/1091-7640 online DOI: 10.1080/10893950490272939 THE DISPARATE THERMAL CONDUCTIVITY OF CARBON NANOTUBES AND DIAMOND NANOWIRES STUDIED BY ATOMISTIC SIMULATION J. F. Moreland and J. B. Freund Theoretical and Applied Mechanics, University of Illinois at Urbana-Champaign, Urbana, IL, USA G. Chen Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA Molecular dynamics simulations were used to calculate the thermal conductivity of carbon nanotubes and diamond nanowires with atomic interactions modeled by the Brenner po- tential. The dependence of thermal conductivity on length, temperature, and temperature “boundary” condition was investigated. Lengths from 50 nm to 1 µ m were simulated at a temperature of 290 K, and additional simulations were performed at 100 K and 400 K, for the 100 nm length. Thermal conductivity was found to be significantly suppressed for the shorter lengths. Two different artificial thermostats were used to impose the temperature difference: one rescaled velocities (the Berendsen thermostat), the other assigned veloci- ties sampled from the appropriate Boltzmann distribution to randomly selected atoms for each numerical time step (the Andersen thermostat). Thus, the Berendsen thermostat am- plifies existing atomic motions, while the Andersen thermostat, in a sense, disrupts the atomic motions. Nevertheless, results were very similar. All simulations were run for at least 200,000 time steps of 1 fsec each. INTRODUCTION The thermal characteristics of carbon nanotubes [1] will be important for designing systems that might incorporate them. Applications in microelectronics are under intense investigation. As with any small electronics, the thermal properties of nanotubes are expected to be important. This study investigates the dependence of thermal conductivity on length and temperature for a (10,10) “armchair” nanotube [1]. See Harris [2] for a complete discussion of the structure of nanotubes [1]. Although thermal transport at these scales can be quite different than at macroscales, we follow the common practice of couching the discussion in the language of continuum heat transfer, particularly in our use of thermal conductivity in describing energy transport properties. Received 2 May 2002; accepted 7 October 2002. This paper was presented at the Intenational Symposium on Micro/Nanoscale Energy Conversion and Transport on April 14–19, 2002 at Antalya, Turkey. Address correspondence to J. B. Freund, 216 Talbot Lab, 104 S. Wright Street, Urbana, IL 61801, USA. E-mail: jbfreund@uiuc.edu 61 62 J. F. MORELAND ET AL....
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THE DISPARATE THERMAL CONDUCTIVITY OF CARBON - MTE 8(1)...

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