  We discuss the implementation and results of a recently developed microscopic
method for calculating ion-ion interaction potentials and fusion
cross-sections. The method uses the TDHF evolution to obtain the instantaneous
many-body collective state using a density constraint. The ion-ion potential as
well as the coordinate dependent mass are calculated from these states. The
method fully accounts for the dynamical processes present in the TDHF
time-evolution and provides a parameter-free way of calculating fusion
cross-sections.
