Relationship between bonding characteristic and thermal property of amorphous carbon structure: Ab initio molecular dynamics study

Abstract

In this study, the bonding characteristic and thermal property of amorphous carbon (a-C) structures with different densities (2.0, 2.3, 2.6, 2.9 and 3.2 g/cm3) were investigated using ab initio molecular dynamics (AIMD). The results show that all structural models with different densities constructed are amorphous structures with short-range order, long-range disorder and a weak anisotropy. With the increase of density of a-C structure, the content of sp3-C atoms and degree of amorphization increase. The residual stress of a-C structure also changes from tensile stress to compressive stress with the increase of density. For electronic property and bonding characteristic of a-C structure, with the increase of density of a-C structure, electronic density of states near Ef of a-C structure decreased gradually and the density of states near Ef is mainly contributed by electrons in 2p orbital of sp2-C atoms. With the increase of the density of a-C structure, number of bonds and 3D-nodes increase while the polarity of covalent bond in a-C structure decreases, which is due to the increase of sp3-C atoms. For the thermal stability of a-C structure, the increase of 3-D nodes and the decrease of polarity of covalent bond can improve the thermal stability of a-C structures carbon and the thermal stability of a-C structure with high density is higher than that with low density.