Amorphous Carbon and the Importance of Hybridization on Thermal Properties

Carbon with its polymorphisms: diamond, graphite/graphene, fullerenes or nanotube occupies already a central position in materials science with plethora of potential applications. The physical properties of these polymorphs adding crystalline or amorphous phase are altered significantly. For amorphous carbon a great variety of polymorphism can be obtained due to a wide range of densities, and the combination of the two hybridizations: sp2, sp3 [1]. If the density of amorphous carbon can be easily quantified experimentally, the hybridization is more challenging and may impact the material properties. In this work, we study of amorphous carbon with molecular dynamics using a Stillinger-Weber interatomic potential modified to favor the sp3 hybridization. In particular, we focus on a density of 2.5 g/cm^3. We first validate the potential used on the structural and vibrational properties, and then a cross-analysis of thermal and vibrational properties is performed using a statistical and a wave-packet approach. This allows to separate the diffusive and propagative contributions to the thermal conductivity [2], and show the importance of the transverse vibrations.

[1]C. de Tomas, I. Suarez-Martinez, and N. A. Marks, Carbon 109, 681 (2016).

[2]P. B. Allen, J. L. Feldman, J. Fabian and F. Wooten, Philos. Mag. B 79, 1715 (1999).