  We consider a model (100) interface between two d-wave superconductors. By
solving the Bogoliubov de Gennes equation on a tight binding lattice, we study
the properties of the interface as a function of the interface barrier. We
contrast the two scenarios: (i) an order parameter phase difference of
$\theta=0$ across the interface, and (ii) a phase slip of $\theta=\pi$ across
the interface. We find resonant sub-gap structure in the density of states only
when there is a phase slip present. We show that the local s-wave and ``p-wave
like'' order parameter components are strongly influenced by the barrier
profile and by the phase slip. The temperature dependence of the local p-wave
order parameter follows the underlying bulk $T_c$ for p-wave superconductivity
implying that this could be measured by a suitable tunneling experiment. We
also calculate the Josephson critical current as a function of the strength of
the insulating barrier at the interface.
