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H O Mártin

Publications and source records attributed to H O Mártin.

8 recordsLinked to original sources
PubMed2006

Drift velocity for a chain of beads in one dimension.

The one-dimensional motion of a chain of N beads is studied to determine its drift velocity when an external field is applied. The dependences of the drift velocity with the chain length and field strength are addressed. Two cases are considered, chains with all their beads charged and chains having an end bead charged. In the last case, an analytical expression for the drift velocity is proposed for all N . Results are tested with the help of Monte Carlo simulations.

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PubMed2006

Effects of island disaggregation in growth models.

We introduced two point island models with island disaggregation. In the first one, particles can detach from islands with an odd number of particles and from those with two particles. In the second model, particles can detach from all islands with more than two particles. The scaling exponents are analytically obtained and verified with Monte Carlo simulations. Specially, the power-law scalings of the island and monomer densities are analyzed. Comparison with other models indicates that the models introduced here present different scaling behaviors.

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PubMed2005

Window effect in a discretized model for diffusion of a chain in one dimension.

We introduce a model to study the diffusion of chains in microporous solids. The difficulties a chain has to escape from a pore where it is confined is found to strongly depend on the ratio between the chain length and the cage size. This dynamic effect implies a nonstandard behavior of the diffusion coefficient. We found a window effect that can be explained without using any energy argument.

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PubMed2004

Growth model with disaggregation of islands having an odd number of particles.

A simple model of deposition of particles and growth of point islands in a two-dimensional substrate is introduced and studied. The detachment of particles from islands with an odd number of particles can occur with a probability P. The power-law scalings of the island, monomer, and odd island densities are analytically obtained and verified by Monte Carlo simulations. The universality class of the model depends on P, and the island density exponent chi changes from chi=1/3 (for P=0 ) to chi=0 (for P>0 ).

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PubMed2003

Quantum diffusion on a cyclic one-dimensional lattice.

The quantum diffusion of a particle in an initially localized state on a cyclic lattice with N sites is studied. Diffusion and reconstruction time are calculated. Strong differences are found for even or odd number of sites and the limit N--> infinity is studied. The predictions of the model could be tested with microtechnology and nanotechnology devices.

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PubMed2003

Discretized model for diffusion of a chain in one dimension.

With the help of Monte Carlo simulations, the one-dimensional diffusion motion of a chain of N beads is studied to determine its diffusion coefficient and viscosity. We found that the end bead movements with respect to that of the central beads play a key role. There is no memory between bead hops but they become correlated as a consequence of the chain dynamics. This determines the scaling exponents and the relation connecting them. In particular, the scaling exponent for the viscosity can be smaller or greater than 3 but it must scale as N3 in the asymptotic regime (N--> infinity ). We analyze in detail the dynamics of a chain with three beads to explain why the expected relation between diffusivity and viscosity exponents is not satisfied.

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PubMed2001

Effects of the sticking probability on the scaling of the island density in a point island model.

The behavior of the island density exponent chi for a model of deposition, nucleation, and aggregation of particles, forming point islands with a sticking probability p in one dimension, is analyzed. Using Monte Carlo simulation we found that chi depends on p. For p=1 we obtain chi congruent with 1/4, the well-known result for perfect sticking and one-dimensional diffusion. Interestingly, as p is decreased, chi adopts higher values. Possible reasons for this behavior are addressed. The universal result for a one-dimensional diffusion, chi=1/4, is expected to be recovered, for all p, only in the asymptotic regime.

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