Molecular-Dynamics Simulations on Heat Conduction in Peapod

1. Molecular-Dynamics Simulations onHeat Conduction in Peapod Fumio Nishimura Takahiro YamamotoKazuyuki Watanabe Department of Physics, Tokyo University of Science

2. 1.Background • High thermal conductivity of CNT • Application of heat sink Substrate Chip Cu:λ = 400W/mK Carbon nanotube CNT: λ ~ 2000W/mK IC chip Carbon nanotube bump Substrate FujitsuCo.2005 http://jp.fujitsu.com/group/labs/

3. 2.Objectives • Thermal conductivity of peapod E. Z. Noya et al, PRB 70, 115416(2004) • higher • lower • Thermal conductanceof peapod isthan empty CNT. G. Wu and B. Li, PRB 76, 085424(2007) Clarify the effect of van derWaals interaction on the thermal conductivity of peapod.

4. 3.Method • Molecular dynamics • Brennerpotential for covalent bond energy • Lenard-Jones potential for van der Waals interaction W. Brenner,Phys. Rev. B 42, 9458 (1990) J. Che, et al. Theor. Chem. Acc 102, 346 (1999) • Thermostat Nosѐ-Hoover method. Nose, S., J. Chem. Phys. 81, 511 (1984) Hoover, W. G., Phys. Rev. A 31, 1695 (1985)

5. 3.Method • Direct method • Thermal current

6. 5.Result • CNT • (10,10)CNT z • Temperature profile • L dependence of thermal current Jth[nW] temperature[K] z[nm] L[nm]

7. 5.Result • Peapod • C60@(10,10)CNT z • L dependence of thermal current • Temperature profile Jth[nW] temperature[K] • C60 z[nm] L[nm]

8. 5.Result • Thermal conductance • : thermal current □(10,10)CNT■Peapod Κ[nW/K] L[nm] • Thermal conductance decreases due to C60s.

9. 5.Result • Thermal current between C60s z z Thermal current does not flows so much through an array of C60s.

10. 5.Conclusion Ⅰ • Effect of C60s on thermal conductance Thermal conductance of a peapod is lower than a pristine CNT. Because An array of C60 does not open a channel for thermal current but interferes via van der Waals interaction with thermal current flowing through a CNT wall. The present result is compatible with a previous result by G. Wu & B. Li. (PRB 76, 085424(2007))

11. 5.Conclusion Ⅱ • Single C60 under the temperature gradient If there is no temperature gradient at 300K C60 vibrates around equilibrium position.

12. 5.Conclusion Ⅱ • Single C60 under the temperature gradient If there is temperature gradient, C60 transfers from hot side to cold side.

13. 5.Conclusion Ⅱ • Single C60 under the temperature gradient Object Outer CNT Inner CNT • Barreiro, R. Rurali, E.R. Hern´andez, • J. Moser, T. Pichler, L. Forr´o, A. Bachtold, • Science320, 775 (2008)

14. 6.Future works • Varity structures in thicker peapod • HRTEM image and diffraction pattern • MD simulation result of (35,35)-(40,40)DWNT T. Yamazaki, F. Nishimura, et al. Nanotechnology 19, 045702 (2008)

15. 5.Conclusion Ⅱ • Single C60 under the temperature gradient

16. Definition of parameter for VDW • Parameters are respectively defined as and