The approach proposed by Choi and Ihm for calculating the ballistic conductance of open quantum systems is generalized to deal with magnetic transition metals. The method has been implemented with ultrasoft pseudopotentials and plane wave basis set in a DFT-LSDA ab initio scheme. We present the quantum-mechanical conductance calculations for monoatomic Ni nanowire with a single spin reversal. We find that a spin reversal blocks the conductance of d electrons at the Fermi energy of the Ni nanowire. On the other hand, two s electrons (one per each spin) are perfectly transmitted in the whole energy window giving 2G(0) for the total conductance. The relevance of these results in connection with recent experimental data is discussed. (C) 2004 Elsevier B.V. All rights reserved.
