Phase coexistence and complicated dynamics in open catalytic systems

The simplest catalytic system with surface phase transitions in CSTR has been studied. It is shown that the possible number of steady states is directly determined by that of phase coexistence regions on the phase diagram of the adsorption layer.

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Relative stability of icosahedral and cuboctahedral metallic nanoparticles

The size and form of metallic nanoparticles (NPs) significantly affects their adsorptive, chemical, and catalytic activity. One of the most interesting nanoscale size effects is the transition from icosahedral to octahedral forms with growth in the NP size. We compared the stability of icosahedral, decahedral and cuboctahedral NPs made from eight metals Ni, Cu, Rh, Pd, Ag, Ir, Pt, and Au using the local optimization of total energy, which was computed from the tight-binding second moment approximation and quantum Sutton–Chen potentials. The obtained results predicted that the icosahedral form would be most stable for Ni, and least stable for Au. For Rh, and especially for Ir, a strong dependency of the stability of the different forms on the NP size was revealed.     

The effect of three-body interactions on thermal desorption spectra

Thermal desorption spectra are calculated for a one-dimensional chain and for a two-dimensional square lattice using the transfer-matrix technique and Monte Carlo simulations. Lateral interactions of adsorbed particles cause a splitting of spectra. The repulsive three-body interactions are shown to lead to an inequality of the integral intensities of the thermal desorption peaks.     

Stochastic simulation of physicochemical processes performance over supported metal nanoparticles

The statistical lattice model has been proposed which permits one to take into account the change in the shape and surface morphology of the nanoparticle under the influence of the reaction media. The influence of monomolecular and dissociative adsorption on the particles equilibrium shape and surface morphology has been studied. It has been shown that by taking into account of attraction "adsorbate-metal" the reshaping of the initial hemispheric particle into cone-shaped one occurs induced by adsorption, similar to the experimentally observed reversible reshaping of active nanoparticles. The model reaction A+B(2) has been studied taking into account the roughening of the active particle surface and the spillover phenomena of the adsorbed A(ads) species over the support surface.     

Influence of lateral interactions on the kinetic characteristics of monomolecular adsorption

The influence of paired lateral interactions on the characteristics of monomolecular adsorption (the rate constant, energy of activation, preexponential factor) was considered. The calculations were carried out by the transfer-matrix method. The possibility was shown of a nonmonotonic dependence of the desorption constant and the activation energy. The data obtained were compared with the calculation results obtained by the Monte Carlo method.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 28, No. 1, pp. 47–52, January–February, 1992.The authors wish to express their gratitude to V. I. Elokhin, V. P. Zhdanov, L. V. Lutevich, and V. D. Sokolovskii for helpful advice and discussions.     

Criterion of multiplicity of steady states and the explicit expression for bifurcation set in the simplest model of a catalytic reaction with an arbitrary isotherm

The following criterion of multiplicity of steady states (m.s.s.) for the simplest model of an open heterogeneous catalytic system (monomolecular isomerization in CSTR) with an arbitrary isotherm was obtained in this paper:

Models of phase transitions for adsorption of simple molecules on metal and oxide surfaces

The well known transfer-matrix method (TMM) of statistical physics is applied to different solid systems, namely metals and oxides. The method is very effective for understanding surface phase transitions in adsorption processes.