An improved approach for obtaining thermodynamic descriptions of intermetallic phases: application to the Cr-Ta system

Some shortcomings of phenomenological phase diagram calculations are addres sed in the present note: (i) the formalism currently used for describing or dered intermetallic phases and (ii) the criteria used for assessing the qua lity of a thermodynamic description. It is shown how the formalism used for ordered intermetallic phases can be improved by replacing the use of subla ttice L parameters with a configurational independent term, which has its p hysical origin in the atomic size mismatch of the participating elements. I t is also suggested that an examination of solid state phase diagrams provi des an additional criterion for the acceptance of good thermodynamic descri ptions over the criteria used at present. The Cr-Ta system is used as an ex ample to show how this improved approach can be used to enhance the quality of the phenomenological thermodynamic modelling of ordered intermetallic p hases. (C) 2001 Elsevier Science Ltd. All rights reserved.