Disordered flat phase and phase diagram for restricted solid-on-solid models of fcc (110) surfaces

Abstract

We discuss the results of a study of restricted solid-on-solid model hamiltonians for fcc (110) surfaces. These models are simple modifications of the exactly solvable BCSOS model, and are able to describe a (2 × 1) missing-row reconstructed surface as well as an unreconstructed surface. They are studied in two different ways. The first is by mapping the problem onto a quantum spin-1/2 one-dimensional hamiltonian of the Heisenberg type, with competing S z i S z j couplings. The second is by standard two-dimensional Monte Carlo simulations. We find phase diagrams with the following features, which we believe to be quite generic: (i) two flat, ordered phases (unreconstructed and missing-row reconstructed); a rough, disordered phase; an intermediate disordered flat phase, characterized by monoatomic steps, whose physics is shown to be akin to that of a dimer spin state. (ii) a transition line from the (2 × 1) reconstructed phase to the disordered flat phase showing exponents which appear to be close, within our numerical accuracy, to the 2D-Ising universality class. (iii) a critical (preroughening) line with variable exponents, separating the unreconstructed phase from the disordered flat phase. Possible signatures and order parameters of the disordered flat phase are investigated.

Simulation of adsorbate-induced faceting on curved surfaces

“…This is the firstorder phase transition and the energy difference is equal to the latent heat. Behaviors of E and dh 2 indicate that this phase transition differs from the roughening phase transition [21,[24][25][26] which belongs to the universality class of KosterlitzThouless transition.…”

Preroughening, fractional-layer occupancies, and phase separation at a disordered flat metal surface

“…In particular, thermal deconstruction of (1ϫ2) surfaces, e.g., Au͑110͒, is believed to lead to a stable DOF phase below roughening. 2,8 So far, on the other hand, no clear evidence of PR has been reported for unreconstructed, i.e., (1ϫ1) metal surfaces, like Ag, Cu, and Ni͑110͒. Various SOS models predict the possibility of PR for these faces, at least under favorable conditions.…”

Solid-on-solid model of overlayer-induced faceting

“…In a SOS model not all atoms from column tops are surface atoms. Therefore in calculation of diffracted intensity sometimes the shadowing factor is used 15 . In this paper we consider the contribution to S only from surface atoms.…”

“…One of approaches to such problems is application of simple solid-on-solid models 11,12,13,14 , in which the crystal is represented by two-dimensional array of columns. They were employed to study roughening transition 11,12 , missingrow reconstruction 15 , growth of the surface 12 , surface diffusion 12,16 , adsorption 14 , phase transitions in two component crystal 13 , etc.…”