Density of states calculations of small diameter single graphene sheets

The densities of slates for the pi-band of single graphene sheets with small diameters were calculated by employing a linear combination of atomic orbital approach using as the basis set the carbon rho(z) atomic orbitals together with a modified Huckel approximation wherein the overlap integrals out to the fourth nearest neighbors set were included. These densities of states were used to predict the voltage of lithiated carbon vs, lithium metal, an important characteristic for disordered carbon used as the negative electrode in rechargeable lithium-ion batteries. Calculations were made for isolated single graphene sheets, C-n, with n = 24, 54, 96, 150, and 216. The results suggested that the lowest voltage should occur for lithiated carbon electrodes composed of single graphene sheets with the smallest diameter (approximate to 0.7 nm for C-24).