Effect Of Substitutional Disorder Research Articles

Raman spectra of CuGaS2-x Se x (x=0, 0.5, 1.0)

Raman spectra on the CuGaS2-x Se x system (x=0, 0.5, 1.0) are described for the first time. The observed structures are assigned on the basis of the analogies with binary solid solutions. The broadening of theA 1 sulphur mode seems to indicate the effect of substitutional disorder.

Ten-fold degenerate d-electron correlation and the metal-nonmetal transition in a disordered binary system: Inclusion of Hund's rule coupling

The Yonezawa-Watabe (YW) study of the metal-nonmetal transitions in nondegenerate, s-electron disordered binary systems: doped semiconductors, metal-ammonia solutions, liquid metals and mixed crystals (alloys), is generalized to include ten-fold d-electron (hole) degeneracy. Such degeneracy automatically includes Hund's rule d-electron coupling and intra-site enhanced Coulomb and exchange interactions. Such a calculation is specifically relevant only to transition metal alloys, transition metal oxides and mixed transition metal oxides. It is seen that potential fluctuations exist in these systems and the possibility of Anderson localization in these disordered degenerate binary transition metal systems is explored. The YW CPA treatment of the effect of substitutional disorder (alloying) upon the mobility gap and quasiparticle states of the density of states at the extreme band edges and localization due to random spin configuration are generalized to these degenerate d-electron systems and it is shown that the disappearance of the mobility gap, not the density of states gap, causes the metal-nonmetal transition for degenerate d-electrons.

Electronic structure of semiinfinite crystals with substitutional disorder in surface layer

The effect of substitutional disorder in the surface atomic layer on the electronic density of states at and near the surface of a semiinfinite crystal is demonstrated on a one band model using the CPA averaged crystal orbital (tight-binding) resolvent with natural boundary condition. For numerical work the separable case of the 100 face in cubium is used.

Thermodynamics and Defect Chemistry of Some Oxide Solid Solutions Part I: Nearest‐Neighbour Interactions and the Effect of Substitutional Disorder

AbstractThis paper is concerned with solid solutions of two isostructural ionic oxides. Relations are derived between activities and composition on the assumption that nearest‐neighbour interactions only are involved. For the solutions under discussion the consequences of this assumption are that the distribution of the cations present in any sublattice is random and that the activity of each kind of cations in a particular sublattice is equal to its concentration in that sublattice. The proof is given that such solutions will be ideal, if they show no substitutional disorder. A comparison is made with some experimental data given in the literature. Three types of disorder may in principle be present simultaneously in binary solutions of the spinels Mn3O4, Fe3O4 and Co3O4. (a) Exchange of electrons between cations of one element on different sites. (b) Exchange of electrons between cations of different elements. (c) Preference of the cations of one element for tetrahedral or octahedral sites. On the basis of these assumptions equations are derived controlling the equilibria which correspond to these types of disorder. A study of the literature shows that the system Mn3O4‐Co3O4 obeys these equations. This is not the case with the systems Fe3O4–Co3O4 and Fe3O4–Mn3O4. The possible reasons for this discrepancy between theory and experiment are discussed and lead to a more general theory, which will be presented in Part II.

The effect of substitutional disorder in the spinel structure upon the x-ray diffraction line profiles

Following Wilson's expression for the variance of a diffraction line profile broadened by mistakes, a simple experimental test for randomness is proposed. The same theory applied to the special case of substitutional disorder in spinel suggests a criterion for homogeneity in structures of mixed composition and methods of distinguishing one type of mistake structure from another.