  Two kinds of simulated bilayers are described and the results are reported
for lateral tension and for partial contributions of intermolecular forces to
it.Data for a widest possible range of areas per surfactant head, from tunnel
formation through tensionless state, transition to floppy bilayer,to its
disintegration, are reported and discussed. The significance of the tensionless
state, is discussed. Conclusions: (1) the tensionless state is a
coincidence;(2) the transition from extended to floppy bilayer occurs nearby
and has hallmarks of a phase transition (3) there is no theory of that
transition.(4)The lateral tension of the floppy bilayer scales with size; that
of the extended bilayer does not depend on size. (4) The drumhead model not
appropriate for interfaces as these fluctuate via diffusion.(5) The radius of
gyration also! shows a discontinuity.
