First-principles electronic structure and transport calculations in materials with defects and impurities.

摘要

We present electronic structure and electron transport studies of materials with defects and impurities using density-functional theory. We develop a plane wave transport method based on density-functional theory for low symmetry nonorthogonal lattices. This is achieved by generalizing Choi and Ihm's algorithm for high symmetry lattices which requires the transport direction along a lattice vector that must be perpendicular to the basal plane formed by two other lattice vectors. This restriction is overcome in our method, allowing solutions to problems in which the transport direction is not along any lattice vectors. We apply our generalized transport method to calculate interface resistivity of grain boundaries in copper. Other than surface defects, we also study point defects such as single atom vacancy and impurities. Using electronic structure methods, we investigate adsorption of gold and iron clusters on perfect and defected graphene with a single vacancy. We focus on the size dependence of the electronic properties such as binding energy, charge transfer, magnetization, and density of states. Perfect graphene is found to be doped for Au clusters with an odd number of atoms and undoped with an even number of atoms. An odd-even oscillation in the magnetic moments is observed in Au-perfect as well as defected graphene system. While Fen clusters remain to be magnetic for all n, the spin of a single Fe atom on a defect site is very small due to a covalent bonding to C atoms.