| In this thesis we outline the mathematical principles behind density functional theory, and describe the iterative Kohn-Sham formulation for computation of electronic density calculations in nano devices. The model for computation of the density of electrons in such device is a non-linear eigenvalue problem that is solved iteratively using the resolvent formalism. There are several bottlenecks to this approach and we propose methods to resolve them. This iterative method involves a matrix inversion. This matrix inversion is called upon when calculating the Green's function for a particular system, the two-probe device. A method to speed up this calculation is to use a preconditioning technique to accelerate the convergence of the iterative method. Tests the existing algorithm for a one-dimensional system are presented. The results indicate that these preconditioning methods reduce the condition number of the matrices. |
