ROUGHENING-INDUCED DECONSTRUCTION IN (100) FACETS OF CSCL-TYPE CRYSTALS

The staggered six-vertex model describes the competition between surfa ce roughening and reconstruction in (100) facets of CsCl-type crystals . Its phase diagram does not have the expected generic structure, due to the presence of a fully packed loop-gas line. We prove that the rec onstruction and roughening transitions, cannot cross nor merge with th is loop-gas line if these degrees of freedom interact weakly. However, our numerical finite size scaling analysis shows that the two critica l lines merge along the loop-gas line, with strong-coupling scaling pr operties. The central charge is much larger than 1.5 and roughening ta kes place at a surface roughness much larger than the conventional uni versal value. It seems that additional fluctuations become critical si multaneously.