Revisiting the electronic properties of diamond-like amorphous carbon

We present results for the electronic properties of diamond-like amorphous carbon obtained using first principles molecular dynamics (FPMD) and including nuclear quantum effects (NQEs) by coupling FPMD with a quantum thermostat.  We carry out simulations with a protocol recently applied to crystalline diamond and molecular carbon [1]. We show that NQEs lead to a substantial renormalization of the fundamental and mobility gaps below 500 K, due to electron-phonon interaction, and that their inclusion in first principles calculations is critical to obtain a reliable physical picture of the electronic structure of diamond-like carbon. Surprisingly, despite the presence of localized electronic states near the HOMO-LUMO gap, in diamond-like carbon the electron-phonon renormalization can be as large as in crystalline diamond,  showing great variability depending on the specific atomistic structure (e.g. sp³ to sp² bond ratio) of the sample.

[1] A. Kundu, M. Govoni, H. Yang, M. Ceriotti, F. Gygi and G. Galli, Phys. Rev. Materials 5, L070801.