arXiv subjects

E. P. M. Leiva

Publications and source records attributed to E. P. M. Leiva.

8 recordsLinked to original sources

arXiv2023

Diversity of behavior after collisions of Sn and Si nanoparticles found using a new Density-Functional Tight-Binding model

We present a new approach to studying nanoparticle collisions using Density Functional based Tight Binding (DFTB). A novel DFTB parameterisation has been developed to study the collision process of Sn and Si nanoparticles (NPs) using Molecular Dynamics (MD). While bulk structures were used as training sets, we show that our model is able to accurately reproduce the cohesive energy of the nanoparticles using Density Functional Theory (DFT) as a reference. A surprising variety of phenomena are revealed for the Si/Sn nanoparticle collisions, depending on the size and velocity of the collision: from core-shell structure formation to bounce-off phenomena.

cond-mat.mes-hall↗

arXiv2015

Thermodynamics deposition on curve nanoholes

In this work the thermodynamics of the electrodeposition on nanoholes is analyzed. Different lattice-gas models of nanoholes, from parallelepiped geometry to the empty bulk of a nanoparticle, were considered. The models include curvature on the inner walls. Several stages of deposition are identified. Monte Carlo technique in the Grand Canonical Ensemble is used to determine isotherms, isosteric heat, energy per site, etc. The study is based on different ranges of energies and nanoholes sizes.

cond-mat.mes-hall↗

arXiv2001

2D-Drop model applied to the calculation of step formation energies on a (111) substrate

A model is presented for obtaining the step formation energy for metallic islands on (111) surfaces from Monte Carlo simulations. This model is applied to homo (Cu/Cu(111), Ag/Ag(111)) and heteroepitaxy (Ag/Pt(111)) systems. The embedded atom method is used to represent the interaction between the particles of the system, but any other type of potential could be used as well. The formulation can also be employed to consider the case of other single crystal surfaces, since the higher barriers for atom motion on other surfaces are not a hindrance for the simulation scheme proposed.

cond-mat↗

arXiv2001

Theoretical Considerations of Electrochemical Phase Formation in a Frank-van der Merwe System

Static calculation and preliminary kinetic Monte Carlo simulation studies are undertaken for the nucleation and growth on a model system which follows a Frank-van der Merwe mechanism. In the present case, we consider the deposition of Ag on Au(100) and Au(111) surfaces. The interactions were calculated using the embedded atom model. The process of formation and growth of 2D Ag structures on Au(100) and Au(111) is investigated and the influence of surface steps on this phenomenon is studied. Very different time scales are predicted for Ag diffusion on Au(100) and Au(111), thus rendering very different regimes for the nucleation and growth of the related 2D phases. These observations are drawn from application of a model free of any adjustable parameter.

cond-mat↗

arXiv2000

Model Calculations for Copper Clusters on Gold Electrodes

Using the embedded-atom method, the structure of small copper clusters on Au(111) electrodes has been investigated both by static and dynamic calculations. By varying the size of roughly circular clusters, the edge energy per atom is obtained; it agrees quite well with estimates based on experimental results. Small three-dimensional clusters tend to have the shape of a pyramid, whose sides are oriented in the directions of small surface energy. The presence of a cluster is found to distort the underlying lattice of adsorbed copper atoms.

cond-mat.mtrl-sci↗

arXiv1997

First principles calculations of monolayer compressibilities

We perform high quality, first principles calculations of the properties of Pb and Tl isolated monolayers. Among these, we consider the equilibrium lattice constant, the two dimensional compressibilities and the electronic density. Comparison is made with previous results obtained using more simplified models. The present results represent an improvement concerning the calculated compressibilities; these remaining still lower than the measured values. We speculate that the latter could be due to some corrugation of the monolayer, not considered in the present modeling.

cond-mat↗

arXiv1997

Facilitated alkali ion transfer at the water 1,2-dichloroethane interphase: Ab-initio calculations concerning alkaline metal cation - 1,10-phenanthroline complexes

A series of calculations on the energetics of complexation of alkaline metals with 1,10-phenanthroline are presented. It is an experimental fact that the ordering of the free energy of transfer across the water - 1,2-dichloroethane interphase is governed by the charge / size ratio of the diferent cations; the larger cations showing the lower free energy of transfer. This ordering of the free energies of transfer is reverted in the presence of 1,10-phenanthroline in the organic phase. We have devised a thermodynamic cycle for the transfer process and by means of ab-initio calculations have drawn the conclusion that in the presence of phen the free energy of transfer is governed by the stability of the PHEN/M $^{+}$complex, which explains the observed tendency from a theoretical point of view.

physics.chem-ph↗

arXiv1997

Some theoretical considerations concerning ion hydration in the case of ion transfer between water and 1,2-dichloroethane

Some aspects of direct ion transfer across the water/1,2-dichloroethane are analyzed using a very simple model based on thermodynamic considerations. It was concluded that ion solvation by water molecules may occur in some particular cases in the organic phase, delivering an important contribution to the Gibbs free energy of ion transfer between the aqueous and the organic phase. In general terms, this particular type of transfer should be favored in the case of highly charged small ions at interfaces with a relatively low surface tension and a large difference between the reciprocal of the corresponding dielectric constants.

physics.chem-ph↗