On-lattice Model Research Articles

Dynamics of the frustrated ising lattice gas

The dynamical properties of a three-dimensional model glass, the frustrated Ising lattice gas (FILG), are studied by Monte Carlo simulations. We present results of compression experiments, where the chemical potential is either slowly or abruptly changed, as well as simulations at constant density. One time quantities like density and two time quantities like correlations, responses, and mean square displacements are measured, and the departure from equilibrium clearly characterized. The aging scenario, particularly in the case of density autocorrelations, is reminiscent of spin glass phenomenology with violations of the fluctuation-dissipation theorem, typical of systems with one replica symmetry breaking. The FILG, as a valid on-lattice model of structural glasses, can be described with tools developed in spin glass theory and, being a finite-dimensional model, can open the way for a systematic study of activated processes in glasses.

Covering of substrate holes through particle deposition

A methodology is proposed to determine the minimum coating thickness for covering substrate holes through particle deposition. The particle deposition process is carried out with a combined, two-dimensional, on-lattice model, in which both deterministic and nondeterministic driving forces are taken into account. The normalized covering thickness (hc/Dw) is investigated subject to variation in the Peclet number (Pe) and the size of the depositing particle, normalized hole size (Dw/L), and degree of postcontact restructuring allowed. It is found that ballistic particle movement gives a slightly better covering structure for smaller holes while diffusive particle movement much more efficiently covers larger holes. The normalized covering thickness increases with increasing normalized hole size and with decreasing normalized depositing particle size. Postcontact restructuring first improves the covering capability of the depositing particle, but then impairs it if further restructuring is allowed. It is further found that the normalized covering thickness scales with the normalized hole size as hc/Dw∼(Dw/L)E with E=0.67, 0.56, and 0.36 for Pe of infinity, 0.5, and 0.1, respectively.

Mapping of mutation-sensitive sites in proteinlike chains

In this work we have studied, with the help of a simple on-lattice model, the distribution pattern of sites sensitive to point mutations (``hot'' sites) in proteinlike chains. It has been found that this pattern depends on the regularity of the matrix that rules the interaction between different kinds of residues. If the interaction matrix is dominated by the hydrophobic effect (a Miyazawa-Jernigan--like matrix), this distribution is very simple: All the hot sites can be found at the positions with the maximum number of closest nearest neighbors (bulk). If random or nonlinear corrections are added to such an interaction matrix the distribution pattern changes. The rising of collective effects allows the hot sites to be found in places with a smaller number of nearest neighbors (surface) while the general trend of the hot sites to fall into a bulk part of a conformation still holds.

Comparative study of large-scale Laplacian growth patterns.

We investigate the scaling of cluster size with mass for our simulations of diffusion-limited aggregation (DLA) clusters and dielectric-breakdown (DB) clusters of ${10}^{6}$ particles grown on a square lattice, and DLA clusters of ${10}^{6}$ particles grown off lattice. We find that the mass distribution and scaling behavior for the on-lattice DB model are intermediate between those for the on-lattice DLA model and the off-lattice DLA model. We take this as evidence that signatures of lattice anisotropy and the microscopic kinetics of attachment are both manifest at large length scales.