Orientational epitaxy of a wall near the commensurate-incommensurate phase transition

Abstract

The authors consider a physisorbed monolayer of rare gas atoms on graphite near the commensurate-incommensurate (C-I) phase transition. They calculate the energy associated with a small rotation of a wall, to second order in the rotation angle. The wall will be titled with respect to the symmetry axis of the substrate if the two-dimensional compressibility K-1 and the shear modulus mu satisfy K<or approximately=3.8 mu . This condition corresponds to non-central forces between adatoms, and therefore is not fulfilled by the rare gas interatomic interaction. They conclude that the walls created at the C-I transition are not rotated, and that rotation should take place in the I phase.