# How self consistency condition works for a superconductors which is finite and does not have periodic boundary condutions?

So if a superconducting system has periodic boundary conditions the s wave superconducting order parameter calculation by self consistency condition is pretty straightforward.

However what if I have a finite crystal with non periodic boundary conditions. How $\Delta$ is calculated in this case. For BEC there is this Thomas Fermi approximation which can be used in finite systems. How order parameter is calculated for finite BCS system?