  Using a novel thermodynamic integration scheme, we compute the excess free
energy, $\gamma$, of a glass-forming, binary Lennard-Jones liquid in contact
with a frozen amorphous wall, formed by particles frozen into a similar
structure as the liquid. We find that $\gamma$ is non-zero, becoming negative
at low temperature. This indicates that the thermodynamics of the system is
perturbed by the effect of the amorphous wall.
