DECONSTRUCTION AND ROUGHENING TRANSITIONS ON (1X2)PT(110)

We have investigated the Pt(110) surface by He atom scattering. The (1 x 2) deconstruction transition at 1087 K is shown to fall in 2D Ising universality class with antiphase domain walls proliferating predomin antly along the [001] direction. The surface roughening is observed at 1160 +/- 10K through a power law broadening of the anti-phase diffrac tion peak along the [001] direction. The two distinct phase transition confine the temperature range in which the surface is disordered but still bound to a common height level.