Structural, thermodynamic and other associated properties of partially ordered Ag-In alloy

Abstract

Extensive computations have been performed using the Lebowitz solution of hard sphere mixtures as a reference system, and perturbed the hard sphere direct correlation function, Coij(r), with square well attractive tail. We used mean spherical model to compute the total and partial direct correlation functions in the attractive and repulsive regions of the interacting potential of Ag-In alloy at different compositions. The potential parameters were those obtained for pure metals. With these potential parameters (the partial and total) structure factors were evaluated, and then Fourier transformed to get the partial and total radial distribution functions. Further the well-known Bhatia-Thornton correlation Junctions namely the number-number, concentration-concentration, and number-concentration correlation functions have been computed. We also obtained total and partial coordination numbers from partial and total pair correlation functions respectively. With the help of these pair correlation functions we give the distances between atoms namely Ag-Ag, In-In and Ag-In at different compositions of In in Ag-In alloy. It is found that these distances practically remain constant and are independent of composition, which has been attributed to the formation of segregated clusters of atomic dimensions. Using Kirkwood-Buffs equation, compressibillities have been calculated as a function of composition. The temperature derivative of diffusion coefficient for pure constituents has been formulated and the computed results were compared with the available experimental values. With this model the diffusion coefficients and the friction coefficients of the constituents have been obtained through the use of Helfand's trajectory principle with a reasonable success in the alloy as well. It is found that these metals of the alloy tend to segregate. The ratio of diffusion coefficients of the metals in the alloy is almost a constant and is equal to 0.9. This shows that the alloy forms a regular solution in spite of their tendency to segregate. © 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.