Calculation of Excess Stability Functions of Four Binary Alloys

The thermodynamic model based on cluster of two atoms is considered with the view to obtaining Scc(0) and the excess stability function of Scc(0). Concentration-concentration fluctuation; Scc(0) of four binary molten alloys was calculated. The thermodynamic properties of these alloys are evaluated based on cluster of two atoms (A & B) or (B & A). Each system has the view of obtaining concentration-concentration fluctuation; Scc(0) enumerating the low-order atomic correlation in the nearest neighbour shell of liquid binary alloys.The highlights of excess stability functions(ES) of Scc(0) of these alloys were reported. The values of Scc(0) for all these alloys are higher than the ideal solution values. The values of Scc(0) for Bi-Cd alloy is close to the ideal Scc (0). The indication of the excess stability of Scc(0) for some alloys is in support of homocoordination. The Scc(0) and excess stability function of Scc (0) for the four alloys are presented. Keywords: Concentration-concentration fluctuation, Excess stability function, Ordering energy.

Calculation of Darken Stability Functions of Al-In and Bi-Zn Binary Liquid Alloys

The thermodynamic model based on clustering of two atoms is considered with the view to obtain the concentration-concentration fluctuation, Scc(0) and the darken stability function. The thermodynamic properties of these alloys were evaluated based on clustering of two atoms (A & B) or (B & A). Each system has the view of obtaining concentration-concentration fluctuation, Scc(0) enumerating the low-order atomic correlation in the nearest neighbour shell of liquid binary alloys. The highlights of reciprocals of Scc(0) of these alloys were noted . The values of Scc(0) for Al-In alloy throughout the entire concentration were positive and higher for activity ratio and lower than the ideal solution values for free energy of mixing at specific Al composition. The values of darken stability function of Al-In alloy fall below the ideal darken stability function for activity ratio and free energy of mixing . The indication of the reciprocal of Scc(0) for all the alloys is in support of homocoordination / heterocoordination in the nearest neighbour shell. The Scc(0) and darken stability function of Bi-Zn binary alloys were noted with fluctuations. Keywords: Concentration-concentration fluctuation, Darken stability function, Ordering energy.

On the Nanostructure of Cu in TixCu1-x and TiN/Cu Films: A XAFS Study

The effect of chemical composition on the bonding environment of Cu, in a series of Ti1-x Cux and TiN/Cu films, is studied using X-Ray Absorption Spectroscopies (XAFS) at the Cu-K-edge. The EXAFS analysis reveals that in all studied samples Cu is amorphous. However, its bonding environment depends on the chemical composition. More specifically, in the Ti1-xCux films, Cu is coordinated with Ti and Cu and belongs both to intermetallic TiCu and to an amorphous Cu matrix. The coordination number of Cu, i.e., the sum of Ti and Cu first neighbours, increases systematically from 6.3 ± 0.7 to 10.6 ± 0.9 when the Cu content increases from 24.1 to 52.7 at%. On the contrary, in the TiN/Cu films, the type of atoms that consists the 1st nearest neighbour shell of Cu varies as a function of the Cu concentration. More specifically, in the TiN/Cu film with the lowest Cu content (27.3 at%), intermetallic TiCu is detected. At intermediate Cu concentration (37.8 at%), Cu is bonded to both Ti and Cu atoms. Finally, in the TiN/Cu film with the highest Cu content (67.7 at%), Cu is metallic.

Magnetic Correlations in Spin Glasses above the Freezing Temperature investigated by High Field Mössbauer Spectroscopy

The strong dynamics of magnetic correlations are observed by high field 57Fe Mössbauer investigations for the spin glasses AuFe and Y(Fe, Al)2 in the temperature interval between the freezing temperature Tf and approximately 7 to 10Tf. All recorded spectra can be analysed with a model which takes into account these dynamics by allowing the formation of correlated states after a stochastically varying time τoff and their decay after a time τon, restricting the number of subspectra to the different number of Fe atoms in the first neighbour shell. Whereas for the different Fe environments, in addition to centre shift and quadrupole splitting, different hyperfine fields of the two stochastically formed states can always be resolved, the same set of τon and τoff values was obtained for all subspectra above approximately 4Tf. The external field hinders the decay of the correlated regions. The temperature dependence of ¿ on scales with Tf and exhibits a power law with exponents of –2 for the Fe-rich and –1 for the Fe-poor compounds.

Structure Investigation on Liquid Tellurium by X-Ray and Neutron Scattering

We present the results of neutron and X-ray scattering experiments on liquid tellurium. No dependence on temperature of the radius and the coordination number of the first neighbour shell has been found in the temperature range between 460 °C and 550 °C. We investigate the influence of the truncation of the Fourier transformation on the determined coordination number of nearest neighbours and on the shape of the second coordination maximum at both, the lower and upper integration limit. The structure of liquid tellurium can be described in terms of a chain-like atomic arrangement with two bonds per atom

Interactions between Nd 3+ ions beyond the first neighbour shell in LaCl 3 and LaBr 3

Some components of the A ij interaction tensors for 3rd to 7th neighbouring Nd 3+ ions in LaCl 3 and LaBr 3 have been measured by means of e. p. r. There are some appreciable super­ exchange contributions to these interactions. The trends in the variation from one neigh­bour to another were unexpected, 4th and 5th neighbours having much larger superexchange than 3rd neighbours. LaBr 3 is similar to LaCl 3 except that the exchange contributions are somewhat larger in LaBr 3 , corresponding to larger covalent overlap. The qualitative features of the measured exchange interactions are explained in terms of the details of the super­exchange paths. For 7th neighbours the interaction is purely dipolar, and it seems likely that more distant neighbours will also have purely dipolar interactions.