Calculation of chemisorption and absorption induced surface segregation
TL;DR: Using a pair bond type model for the interatomic interactions, the authors determined surface segregation on clean, H, O and CO covered surfaces of various alloys and studied surface segregation caused by bulk hydrogen absorption.
About: This article is published in Surface Science.The article was published on 1982-01-02. It has received 124 citations till now. The article focuses on the topics: Chemisorption & Absorption (chemistry).
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TL;DR: A review of core-level binding energy shifts observed in photoelectron spectroscopy can be found in this paper, where the authors focus on shifts since most of the chemical and physical insights provided by core levels are derived not from the core energies themselves but from shifts they exhibit.
588 citations
TL;DR: In this article, the best anode electrocatalysts, mainly the alloys, which have been tested in direct liquid-feed fuel cells fed with methanol, ethanol or formic acid.
243 citations
TL;DR: The optical properties of Au–Ag nanoparticles show the control that can be achieved in the tuning of the local surface plasmon resonance, depending of the alloy content, the chemical ordering, the morphology, the size of the nanoparticle, and the nature of the surrounding environment.
Abstract: The alloy Au–Ag system is an important noble bimetallic phase, both historically (as “Electrum”) and now especially in nanotechnology, as it is applied in catalysis and nanomedicine. To comprehend the structural characteristics and the thermodynamic stability of this alloy, a knowledge of its phase diagram is required that considers explicitly its size and shape (morphology) dependence. However, as the experimental determination remains quite challenging at the nanoscale, theoretical guidance can provide significant advantages. Using a regular solution model within a nanothermodynamic approach to evaluate the size effect on all the parameters (melting temperature, melting enthalpy, and interaction parameters in both phases), the nanophase diagram is predicted. Besides an overall shift downward, there is a “tilting” effect on the solidus–liquidus curves for some particular shapes exposing the (100) and (110) facets (cube, rhombic dodecahedron, and cuboctahedron). The segregation calculation reveals the pre...
149 citations
TL;DR: In this paper, the catalytic activity of Ni and Ni/Ni/Cu(100) with respect to the methanol synthesis from various mixtures containing CO, CO, and H{sub 2} was studied in a combined UHV/high pressure cell apparatus at reaction conditions, P = 1.5 bar and T = 543 K.
116 citations
IBM1
02 Mar 1989-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this article, it was shown that the BIS is caused by chemically guided final steps in some ballistic trajectories and that the driving force for segregation is so small, ranging from 0.06 eV to 0.52 eV for AuNi, and that for ambient temperature the inequality K b ⪡ K eq holds.
Abstract: Compositional changes in bombarded alloys are now recognized to arise mainly from bombardment-induced segregation, “BIS” and to only a limited extent from preferential sputtering, i.e. from differences in mass, chemical binding, or volatility. The significant relation is α A (2) α B (2) = (α A (2′) α B (2′) ) K b , where α is the atom fraction, A and B are the components of the alloy, 2 designates atom layer one , 2′ designates atom layer two and K b is the BIS ratio. A very similar relation holds for equilibrium segregation except that K b is replaced with K eq , equivalent to exp ( ΔG seg / kT ). It is shown that K b and K eq are always in the same sense except for NiPt, that K b lies in the interval 1.25 ⩽ K b ⩽ 5.4 for 14 out of 16 different systems and that for ambient temperature the inequality K b ⪡ K eq holds. Most aspects of the relation between K b and K eq can be understood if BIS is caused by chemically guided final steps in some ballistic trajectories. Such a mechanism also accounts for what is otherwise a paradox, namely that the driving force for segregation is so small, ranging from 0.06 eV for CuPd to 0.52 eV for AuNi. The latter values are similar to heats of mixing, proposed by Cheng et al. to govern ion-beam mixing and to differences of heats of formation, proposed by the present author to govern chemical changes in oxides and oxysalts.
97 citations
References
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01 Jan 1973
TL;DR: In this paper, methods of evaluation, atomic weights, fundamental constants, symbols and units, general references, and properties of the elements are presented. But they do not specify the properties of elements.
Abstract: : Contents: Methods of evaluation, atomic weights, fundamental constants, symbols and units, general references, and properties of the elements.
1,987 citations
TL;DR: In this article, the authors present a computer program in Algol 60 by means of which enthalpy effects can be calculated for binary alloys in which at least one transition metal is involved.
Abstract: We present a computer program in Algol 60 by means of which enthalpy effects can be calculated for binary alloys in which at least one transition metal is involved. Predictions can be made by means of this program for seven fixed ordered compositions in the solid phase and for the two limiting heats of solution and the heat of mixing at the equlatomic composition in the liquid phase. For solid alloys the predictions are representative for equilibrium compounds. As an example, we Include the output for combinations of iron and cobalt with all other metals. In addition, we include a complete table of heats of solution in liquid alloy systems. A discussion is given of both the accuracy of the predictions and the differences between predictions and the experimentally observed quantities that vary systematically with the position of the elements in the periodic table.
1,151 citations
TL;DR: In this paper, the authors defined the heat of adsorption as the energy needed to break the MX2 bond and defined ΔHads as the amount of energy required to do so.
Abstract: One of the important physical-chemical properties that characterizes the interaction of solid surfaces with gases is the bond energy of the adsorbed species. The determination of the bond energy is usually performed indirectly by measuring the heat of adsorption (or heat of desorption) of the gas [1, 2], In order to define the heat of adsorption, let us consider the chemisorption of a diatomic molecule, X2, onto a site on a uniform solid surface, M. The molecule may adsorb without dissociation to form MX2. M represents the adsorption site where bonding occurs to a cluster of atoms or to a single atom. In this circumstance, the heat of adsorption, ΔHads, is defined as the energy needed to break the MX2 bond:
306 citations
TL;DR: In this article, thin films of silver, palladium and their alloys prepared by simultaneous sublimation onto Pyrex at 78 K and subsequently equilibrated at 573 K, were investigated by photoelectron emission to gain information on the surface composition by means of the work function (φ) and the emission constant (M).
147 citations