  Potential steps exceeding 1 eV are regularly formed at metal|insulator
interfaces, even when the interaction between the materials at the interface is
weak physisorption. From first-principles calculations on metal|h-BN interfaces
we show that these potential steps are only indirectly sensitive to the
interface bonding through the dependence of the binding energy curves on the
van der Waals interaction. Exchange repulsion forms the main contribution to
the interface potential step in the weakly interacting regime, which we show
with a simple model based upon a symmetrized product of metal and h-BN wave
functions. In the strongly interacting regime, the interface potential step is
reduced by chemical bonding.
