High and anisotropic thermal conductivity of body-centered tetragonal C4 calculated using molecular dynamics

The thermal properties of body-centered tetragonal C₄ (bct-C₄), a new allotrope of carbon, were investigated using molecular dynamics (MD) simulations. The calculations gave a high and anisotropic thermal conductivity that is the first of its kind. The cross-plane thermal conductivity is 1209 W/(m K) at room temperature, which is even higher than that of diamond. The thermal conductivity decreases as the temperature increases from 80 to 400 K. The density of states of bct-C₄ was analyzed, which has a prominent peak at 36 THz. The relaxation times were calculated by fitting a heat flux autocorrelation function. The results showed that the acoustic phonons play the dominant role in the heat conduction, with a contribution of more than 99%. The relaxation times decrease with increasing temperature, as does the contribution of the acoustic phonons. Finally, the thermal conductivity based on lattice dynamics agreed well with that from the MD method, with which the group velocity and mean free path were deduced. This outstanding thermal property makes bct-C₄ a promising substitute for diamond, especially as thermal interface materials in microelectronic packaging.