  Recently the nonlocal coherent-potential approximation (NLCPA) has been
introduced by Jarrell and Krishnamurthy for describing the electronic structure
of substitutionally disordered systems. The NLCPA provides systematic
corrections to the widely used coherent-potential approximation (CPA) whilst
preserving the full symmetry of the underlying lattice. Here an analytical and
systematic numerical study of the NLCPA is presented for a one-dimensional
tight-binding model Hamiltonian, and comparisons with the embedded cluster
method (ECM) and molecular coherent potential approximation (MCPA) are made.
