**Effects of torsion on the thermal conductivity of multi-layer graphene**

C Si and G Lu and BY Cao and XD Wang and Z Fan and ZH Feng, JOURNAL OF APPLIED PHYSICS, 121, 205102 (2017).

DOI: 10.1063/1.4983812

This work employs the equilibrium molecular dynamics method to study the effects of torsion on the thermal conductivity of multi-layer graphene. Thermal conductivities of twisted 10-layer 433.91 x 99.68 angstrom(2) graphene with torsion angles of 0 degrees, 11.25 degrees, 22.5 degrees, 33.75 degrees, 45 degrees, 67.5 degrees, 90 degrees, 112.5 degrees, and 135 degrees are calculated. The corresponding radial distribution functions and nearest atomic distances are calculated to reveal the effects of torsion on lattice structures. The spectral energy density (SED) method is utilized to analyze the phonon transport properties. It is very interesting that the thermal conductivity of multi-layer graphene decreases slightly at first and then increases with the increasing torsion angle, and the valley is located at theta(G) = 22.5 degrees with the lowest thermal conductivity of 4692.40W m(-1) K-1. The torsion effect can be considered as a combination of the compression effect and the dislocation effect. Further SED analysis confirms that the effect of dislocation on thermal conductivities can be negligible, while the compression effect decreases the phonon lifetimes of flexural out-of-plane acoustic (ZA) branches and increases the ZA group velocities and the phonon specific heat. The decrease becomes dominated when the torsion angle is small, whereas the increase becomes more and more dominated when the torsion angle becomes larger, which are responsible for the reported variation of thermal conductivities. Published by AIP Publishing.

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