  A density functional theory based two-terminal scattering formalism that
includes spin-orbit coupling and spin non-collinearity is described. An
implementation using tight-binding muffin-tin orbitals combined with extensive
use of sparse matrix techniques allows a wide variety of inhomogeneous
structures to be flexibly modelled with various types of disorder including
temperature induced lattice and spin disorder. The methodology is illustrated
with calculations of the temperature dependent resistivity and magnetization
damping for the important substitutional disordered magnetic alloy Permalloy
(Py), Ni$_{80}$Fe$_{20}$. Comparison of calculated results with recent
experimental measurements of the damping (including its temperature dependence)
indicates that the scattering approach captures the most important
contributions to this important property.
