  The dynamics of the normal/superconducting interface in type-I
superconductors has recently been derived from the time-dependent
Ginzburg-Landau theory of superconductivity. In a suitable limit these
equations are mapped onto a ``free-boundary'' problem, in which the interfacial
dynamics are determined by the diffusion of magnetic flux in the normal phase.
The magnetic field at the interface satisfies a modified Gibbs-Thomson boundary
condition which involves both the surface tension of the interface and a
kinetic coefficient for motion of the interface. In this paper we calculate the
surface tension and kinetic coefficient numerically by solving the one
dimensional equilibrium Ginzburg-Landau equations for a wide range of $\kappa$
values. We compare our numerical results to asymptotic expansions valid for
$\kappa\ll 1$, $\kappa\approx 1/\sqrt{2}$, and $\kappa\gg 1$, in order to
determine the accuracy of these expansions.
