  We develop a method to solve the Bogoliubov de Gennes equation for
superconductors self-consistently, using the recursion method. The method
allows the pairing interaction to be either local or non-local corresponding to
s and d-wave superconductivity, respectively. Using this method we examine the
properties of various S-N and S-S interfaces. In particular we calculate the
spatially varying density of states and order parameter for the following
geometries (i) s-wave superconductor to normal metal, (ii) d-wave
superconductor to normal metal, (iii) d-wave superconductor to s-wave
superconductor. We show that the density of states at the interface has a
complex structure including the effects of normal surface Friedel oscillations,
the spatially varying gap and Andeev states within the gap, and the subtle
effects associated with the interplay of the gap and the normal van Hove peaks
in the density of states. In the case of bulk d-wave superconductors the
surface leads to mixing of different order parameter symmetries near the
interface and substantial local filling in of the gap.
