Solid solutions ordered

The layer of titanium and ruthenium oxides usually is applied to a titanium substrate pyrolytically, by thermal decomposition (at a temperature of about 450°C) of an aqueous or alcoholic solution of the chlorides or of complex compounds of titanium and rathenium. The optimum layer composition corresponds to 25 to 30 atom % of ruthenium. The layer contains some quantity of chlorine its composition can be written as Ruq 2sTio 750(2- c)Cl r At this deposition temperature and Ru-Ti ratio, the layer is a poorly ordered solid solution of the dioxides of ruthenium and titanium. Chlorine is completely eliminated from the layer when this is formed at higher temperatures (up to 800°C), and the solid solution decomposes into two independent phases of titanium dioxide and ruthenium dioxide no longer exhibiting the unique catalytic properties. 

Consider the A-B binary system. If A and B form a random solid solution with, say, 10 atom percent B, the probability of finding a B atom on any specific lattice site is just 0.1. Under certain conditions, however, B atoms may favour certain specific sites than die test. B atoms will then preferentially position themselves on these specific sites. The probability of finding B atoms in these sites will greatly increase. This type of arrangement is referred to as an ordered structure. The process in which a random disordered solid solution is rearranged into an ordered solid solution is called an order-disorder transition. 

Random versus Partially Ordered Solid Solutions.—One of the points that needed to be clarified in order to understand the nature of the interactions at the microscopic level within the disordered phase is whether the heterochiral molecules are randomly distributed in the crystals, in which case the contacts are of (RR), (SS), and RS) natures, or if they are ordered in homochiral stacks, where the contacts are mainly of (RR) and (S5) natures. ... 

Turning to the crystal structure of compounds of unlike atoms, we find that the structure is built up on the skeleton of a Bravais lattice but that certain other rules must be obeyed, precisely because there are unlike atoms present. Consider, for example, a crystal of A Bj, which might be an ordinary chemical compound, an intermediate phase of relatively fixed composition in some alloy system, or an ordered solid solution. Then the arrangement of atoms in A By must satisfy the... 

Still another type of structure worth noting is that of ordered solid solutions. As described above, a typical substitutional solid solution has solute atoms distributed more or less at random on the lattice points of the solvent.f On the other hand, there are solutions in which this is true only at elevated temperatures when cooled to lower temperatures, the solute atoms take up an orderly, periodic... 

We have already seen that the intensity of a superlattice line from an ordered solid solution is much lower than that of a fundamental line. Will it ever be so low that the line cannot be detected We can make an approximate estimate by ignoring the variation in multiplicity factor and Lorentz-polarization factor from line to line, and assuming that the relative integrated intensities of a superlattice and fundamental line are given by their relative F values. For fully ordered AuCus, for example, we find from Eqs. (13-1) that... 

When Se and Sio are dissolved together in CS2 and the solution is cooled, then, under special concentration conditions, a stoichiometric well ordered solid solution of the two components crystallizes as orange-yellow opaque crystals of m.p. 92 [34]. The structure of Se-Sio consists of alternating lay-... 

DFT studies of binary hard-sphere mixtures predate the simulation studies by several years. The earliest work was that of Haymet and his coworkers [221,222] using the DFT based on the second-order functional Taylor expansion of the Agx[p]- Although this work has to some extent been superceded, it was a significant stimulus to much of the work that followed both with theory and computer simulations. For example, it was Smithline and Haymet [221] who first analyzed the Hume-Rothery rule in the context of hard sphere mixture behavior and who first investigated the stability of substitutionally ordered solid solutions. The most accurate DFT results for hard-sphere mixtures have come from the WDA-based theories. In particular the results of Denton and Ashcroft [223] and those of Zeng and Oxtoby [224] give qualitatively correct behavior for hard spheres forming substitutionally disordered solid solutions. 

Joe. 24.—Effect of Composition on Electrical Resistance and Hardness of Copper-Gold Alloys (a) Quenched. 1 )isordoied-Solid Solution, (b) Slowly Cooled. Ordered-Solid Solution. 

Fio. 25.—Complete Ordered-Solid Solution, containing 75 Atomic per cent, ( u and 25 Atomic per cent. An. 

Open metals, OH Ordered solid solution, 78, 80, 82 — solutions and intermetallic compounds, 80... 

The goal of the addition of a secondary metal is to enhance activity and/or stability. Adatoms are adsorbed onto preformed catalyst surfaces. While for both alloys and intermetallics, the composition of a base metal (typically R or Pd) is altered by the addition of a secondary metal as part of the preparation procedure. The key difference between the two is that alloys are characterized by a random mixture of at least two metallic solid solution phases, while intermetalUcs are defined as ordered solid solution phases with fixed stoichiometry and identical atomic unit cells. The resulting intermetallics have uniform geometries, resulting in control of the electronic environment [16]. 

The standard periodic ab-initio approach could be used only for ground-state energy calculations and ordered structures and thus does not allow prediction of thermodjmamic stability of these phases as the temperature grows. This forces the problem to be reformulated so as to permit the extraction of the necessary energy parameters from the calculations for the ordered phases, and to apply these parameters to the study of the disordered or partly ordered solid solutions, in order to get information on the thermodynamic behavior of LSM solid solutions. Prom the exper-... 

At the composition Bi43Tes7 Brebrick detected even one phase with 3 x 85 layers (c = 513,08 A) and a second one with 3 x 86 layers (c = 519.20 A). These phases represent a rather unusual type of ordered solid solutions and remind one of the valleriite-related minerals CuFeS2 Mg(OH)2, FeS-nMg(OH)2 etc. 

Correlations between the Structure of Ordered Solid Solutions and Parameters of Pair Interactions in Perovskites... 

Correlations between the Strueture of Ordered Solid Solutions... 

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