Cohesive and electronic properties of Ni-(In,Sn) intermetallics: ab-initio database and systematics

S. RAMOS DE DEBIAGGI

La Plata

Workshop; 4th Workshop on novel methods for electronic structure calculations, and First Southamerican Congress on Materials; 2011

Universidad Nacional de la Plata

A comprehensive study of the equilibrium structural, cohesive and electronic properties of intermetallic phases (IPs) of the Ni-(In-Sn) systems, have been performed by ab initio density-funcional-theory (DFT) methods. The properties of these materials are currently a subject of considerable theoretical and experimental interest in connection with the application of In-Sn alloys as lead-free micro-soldering alloys when Ni is the contact material. A particular motivation for the current research efforts is the general lack of experimental information on the physico-chemical properties which are of great importance for defining the final properties of the joints, a problem that involves  the thermophysics of the various relevant IPs of these systems. A first purpose of this contribution is to report a detailed first-principles characterisation of various stable Ni-In and Ni-Sn phases. Another purpose of the present work is to present advances on the use of ab initio methods for developing a specific database with theoretical information on the relevant IPs which is important in connection with the thermodynamic analysis of the Ni-In-Sn system using thermodynamic models and the so-called CALPHAD techniques. Using the VASP code [1] with the projector augmented wave potentials we have performed systematic ab initio DFT calculations. Some simple selected phases of the Ni-In system have also been modeled using the DFT all electron Full-Potential Linear Augmented Plane Wave method (FP-LAPW) and the Wien2k code [2]. Structural parameters, energies of formation (EOF) from the elements and cohesive properties of the various phases have been established by minimizing the internal structural parameters. Specifically, we present trends in the composition dependence of the 0 K molar volumen, bulk modulus and its pressure derivative, electronic density of states and the EOF of several IPs which are stable in the Ni-In and Ni-Sn binaries. The results are compared with the available experimental data and with previously reported ab initio results. The present study of cohesive and thermodynamic properties of Ni-In/Sn intermetallic phases as well as their trends as functions of composition, should be useful both in the design of new soldering alloys and in the understanding of the phase-stability systematics. [1] G. Kresse, J. Furthmüller, Comput. Mater. Sci. 6 (1996) 15. [2] P. Blaha, K. Schwarz, G.K.H. Madsen, D. Kvasnicka y J.  Luitz, WIEN2k_10, Techn. Universitat Wien, Austria, 2001.