Spin-potential functional formalism for current-carrying noncollinear magnetic systems.

We develop a formalism dual to spin-current-density functional theory (CDFT) where minimization with respect to the scalar and vector spin potentials is used. In this way we circumvent the issues surrounding the nonuniqueness of the mapping between spin potentials and ground-state wave functions, and the v representability issue of current-density functionals. The approach applied within the Kohn-Sham formalism provides the foundations for the optimized effective potential method for CDFT.