  Monte Carlo computer simulations with an embedded-atom potential are applied
to study coherent gamma/gamma' interfaces in the Ni-Al system. The (100)
interface free energy has been extracted from the power spectrum of equilibrium
shape fluctuations (capillary waves) and found to decrease with temperature
from about 20 mJ/m2 at 550 K to about 10 mJ/m2 at 1200 K. These numbers are in
reasonable agreement with existing experimental data. Strengths and
disadvantages of the capillary wave method are discussed.
