Anisotropy of the order-disorder phase transition on the Pb(110) surface

Surface premelting of lead crystals has been examined by the measurement of integrated LEED beam intensity as a function of temperature. In agreement with previous results, surface premelting on the (110) surface begins well below the bulk melting temperature. Surface premelting is anisotropic in that complete disorder is achieved at lower temperature in the [11{}0] direction than in the [001] direction. The interface between the ordered and fully disordered phase is atomically sharp for disorder along [11{}0] but extended along [001], where the substrate acts to preserve partial translational order.