Effect of short-range order on the electronic structure and optical properties of the CuZn alloy : an augmented space approach

In this work we have combined the generalized augmented space method introduced by one of us with the recursion method of Haydock et al (GASR), within the framework of the local density functional based linear muffin-tin orbitals basis (TB-LMTO). Using this we have studied the effect of short-range ordering and clustering on the density of states, optical conductivity and reflectivity of 50-50 CuZn alloys. Our results are in good agreement with alternative techniques. We argue that the TB-LMTO-GASR is a feasible, efficient and quantitatively accurate computational technique for the study of environmental effects in disordered binary alloys.Comment: 11 pages 11 figure

Study of phase stability of MnCr using the augmented space recursion based orbital peeling technique

In an earlier communication we have developed a recursion based approach to the study of phase stability and transition of binary alloys. We had combined the recursion method introduced by Haydock, Heine and Kelly and the our augmented space approach with the orbital peeling technique proposed by Burke to determine the small energy differences involved in the discussion of phase stability. We extend that methodology for the study of MnCr alloys.Comment: 11 page

A systematic investigation of sample diluents in modern supercritical fluid chromatography

This paper focuses on the possibility to inject large volumes (up to 10 L) in ultra-high performancesupercritical fluid chromatography (UHPSFC) under generic gradient conditions. Several injection andmethod parameters have been individually evaluated (i.e. analyte concentration, injection volume, initialpercentage of co-solvent in the gradient, nature of the weak needle wash solvent, nature of the samplediluent, nature of the column and of the analyte). The most critical parameters were further investigatedusing in a multivariate approach. The overall results suggested that several aprotic solvents includingmethyl tert-butyl ether (MTBE), dichloromethane, acetonitrile or cyclopentyl methyl ether (CPME) werewell adapted for the injection of large volume in UHPSFC, while MeOH was generally the worst alternative.However, the nature of the stationary phase also had a strong impact and some of these diluents did notperform equally on each column. This was due to the existence of a competition in the adsorption of theanalyte and the diluent on the stationary phase. This observation introduced the idea that the samplediluent should not only be chosen according to the analyte but also to the column chemistry to limitthe interactions between the diluent and the ligands. Other important characteristics of the “ideal” SFCsample diluent were finally highlighted. Aprotic solvents with low viscosity are preferable to avoid strongsolvent effects and viscous fingering, respectively. In the end, the authors suggest that the choice of thesample diluent should be part of the method development, as a function of the analyte and the selectedstationary phase