First-principles calculation of current density in molecular devices

Abstract

Based on the single-particle nonequilibrium Green's function (NEGF) technique coupled with the density-functional theory (DFT), we investigate the current density distribution of a molecular device Al-${\mathrm{C}}_{60}$-Al from first principles. Due to the presence of nonlocal pseudopotential, the conventional definition of current density is not suitable to describe the correct current density profile inside the molecular device. By using the new definition of current density, which includes the contribution due to the nonlocal potential, our numerical results show that the new definition of current density $\mathbf{J}(\mathbf{r})$ conserves the current. In addition, the current obtained from the current density calculated inside the molecular device equals to that calculated from the Landauer-B\uttiker formula. Finally, for the molecular device Al-${\mathrm{C}}_{60}$-Al, loop currents were found, which confirms the result obtained from the tight-binding approach.