phasebdy
equation_of_state phase_boundary delta_rho delta_e
where the equation of state is any EOS form,
and the phase boundary is a Realfunction2d,
of density and energy, positive in the region of the daughter phase,
and delta_rho and delta_e are Realfunction2ds defining
the offset to apply to the density and energy, each as a function
of density and energy, in the daughter region only.