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, C O ij (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 functions namely the numbernumber, 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-Buff's 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.

Hydrogenations over Silver: A Highly Active and Chemoselective Ag‐In/SiO2 Catalyst for the One‐Step Synthesis of Allyl Alcohol from Acrolein

“…The formation of supported nano-sized alloy structures, which are partially ordered in the case of the macroscopic Ag-In system [18], is a structural peculiarity of the catalyst and can be catalytically interpreted ± analogous to the catalytic activity and chemoselectivity of Laves and Hume-Rothery phases [19] ± as a confirmation of the thesis of the preferred C=O group hydrogenation (in the presence of a C=C bond) over polar active sites, which cause a di-r C=O adsorption configuration of the a,b-unsaturated aldehyde [5].…”

Theoretical evaluation of structural and various associated properties of Al–Si melts

“…The Ashcroft-Langreth partial structure factors S 11 (k), S 22 (k) and S 12 (k) can be obtained by taking the Fourier transformations of h ij (r) given as [11,12] S 11 ðkÞ ¼ f1 À q 1 C 11 ðkÞ À q 1 q 2 C 2 12 ðkÞ=½1 À q 2 C 22 ðkÞg À1 ð4Þ S 22 ðkÞ ¼ ½1 À q 1 C 11 ðkÞS 11 ðkÞ=½1 À q 2 C 22 ðkÞ ð5Þ S 12 ðkÞ ¼ ðq 1 q 2 Þ 1=2 C 12 ðkÞS 11 ðkÞ=½1 À q 2 C 22 ðkÞ ð6Þ and finally obtaining the total structure factor in terms of partial structure factors and concentration as follows…”

“…The mutual diffusion coefficients of the alloy can be evaluated through self-diffusion coefficients. From the temperature derivative of the diffusion coefficients [11,12] of pure components we obtain their activation energies.…”

Hydrierungen mit Silber: Hochaktiver und chemoselektiver Ag‐In/SiO2‐ Katalysator für die Direktsynthese von Allylalkohol aus Acrolein

“…H Die Bildung von geträgerten nanodispersen Legierungstrukturen, die beim makroskopischen Ag-In-System partiell geordnet sind [18], ist eine strukturelle Besonderheit des Katalysators und erscheint ± in Analogie zur Aktivität und Chemoselektivität von Laves-und HumeRothery-Phasen [19] ± in ihrer katalytischen Deutung eine Erhärtung der These von der bevorzugten Hydrierung der C=O-Gruppe (in Anwesenheit einer C=C-Bindung) an polaren Aktivzentren, die eine di-r C=O -Adsorptionskonfiguration des a,b-ungesättigten Aldehyds bewirken [5].…”

“…In [15], p total = 2 ± 4 MPa, T = 453 ± 593 K, WaF AcY0 = 5 ± 30 g Kat hmol ±1 , H 2 /AC = 20 ± 80, Online-GC-Analytik) als auch als Flüssigphasenreaktion (Parr-Rührautoklav, p total = 5 MPa, T = 453 K, m Kat = 0,5 g, c Ac , 0 = 1 mol L ±1 , Offline-GC-Analytik). Die Bildung von geträgerten nanodispersen Legierungstrukturen, die beim makroskopischen Ag-In-System partiell geordnet sind [18], ist eine strukturelle Besonderheit des Katalysators und erscheint ± in Analogie zur Aktivität und Chemoselektivität von Laves-und Hume-Rothery-Phasen [19] ± in ihrer katalytischen Deutung eine Erhärtung der These von der bevorzugten Hydrierung der C=O-Gruppe (in Anwesenheit einer C=C-Bindung) an polaren Aktivzentren, die eine di-r C=O -Adsorptionskonfiguration des a,b-ungesättigten Aldehyds bewirken [5].…”