arXiv subjects

S. Prestipino

Publications and source records attributed to S. Prestipino.

23 records · Page 2Linked to original sources

arXiv2003

Density-functional theory of a lattice-gas model with vapour, liquid, and solid phases

We use the classical version of the density-functional theory in the weighted-density approximation to build up the entire phase diagram and the interface structure of a two-dimensional lattice-gas model which is known, from previous studies, to possess three stable phases -- solid, liquid, and vapour. Following the common practice, the attractive part of the potential is treated in a mean-field-like fashion, although with different prescriptions for the solid and the fluid phases. It turns out that the present theory, compared to similar theories in the continuum, is of worse quality. Nevertheless, at least a number of qualitative facts are reproduced correctly: i) the existence of three phases; ii) the disappearance of the liquid phase when the range of the attraction is progressively reduced; and iii) the intrusion, just below the triple-point temperature, of a liquid-like layer at the interface between the coexisting solid and vapour phases.

cond-mat.stat-mech↗

arXiv2003

Analog of surface preroughening in a two-dimensional lattice Coulomb gas

Elaborating on previous theoretical treatments of the roughening transition, we provide the exact mapping of a surface model which undergoes both roughening and preroughening onto a mixture of unit and double charges living on the square lattice. Depending on the model parameters, the preroughening transition of the surface can be either continuous or discontinuous. Using the surface temperature as a control parameter, the dual Coulomb gas accordingly undergoes two consecutive phase transitions through equilibrium phases whose dielectric behavior is analysed in terms of Monte Carlo simulation and exact finite-size calculations. Right at the preroughening point of the surface model, the charged mixture behaves like an electric insulator (provided preroughening is second-order), while showing metallic behavior below and above that temperature, at least up to the roughening temperature where the conventional metal-insulator transition occurs.

cond-mat.stat-mech↗

arXiv1999

Can one have preroughening of vicinal surfaces?

We discuss the possibility that, besides roughening, a vicinal surface could display preroughening (PR), and consider the possible mechanisms for its promotion. Within the framework of a terrace-step-kink model, it turns out that a PR transition is possible, and could be induced by a short-range repulsion between parallel kinks along the same step or on adjacent steps, or even by some kind of extended range step-step repulsion. We discuss the possible relevance of this phenomenon to the anomalous roughening behaviour recently reported for Ag(115).

cond-mat.stat-mech↗

arXiv1995

Disordered Flat Phase and Phase Diagram for Restricted Solid on Solid Models of Fcc(110) Surfaces

We discuss the results of a study of restricted solid-on-solid models for fcc (110) surfaces. These models are simple modifications of the exactly solvable BCSOS model, and are able to describe a $(2\times 1)$ 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 $S^z_iS^z_j$ couplings. The second is by standard 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 (DF) 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 $(2\times 1)$ reconstructed phase to the DF 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 DF phase. Possible signatures and order parameters of the DF phase are investigated.

cond-mat↗

arXiv1995

Preroughening, Diffusion, and Growth of An FCC(111) Surface

Preroughening of close-packed fcc(111) surfaces, found in rare gas solids, is an interesting, but poorly characterized phase transition. We introduce a restricted solid-on-solid model, named FCSOS, which describes it. Using mostly Monte Carlo, we study both statics, including critical behavior and scattering properties, and dynamics, including surface diffusion and growth. In antiphase scattering, it is shown that preroughening will generally show up at most as a dip. Surface growth is predicted to be continuous at preroughening, where surface self-diffusion should also drop. The physical mechanism leading to preroughening on rare gas surfaces is analysed, and identified in the step-step elastic repulsion.

cond-mat↗