RAMOS susana Beatriz
congresos y reuniones científicas
Structural and thermodynamic effects of incorporating In atoms into the (mC44) Cu6Sn5-type structure phase: Ab initio study, correlations and chemical-bonding trends
Congreso; Discussion Meeting on Thermodynamics of Alloys - TOFA 2016; 2016
Institución organizadora:
Universidad de San Pablo
Along-standing challenge of the physical chemistry of materials is the accurateaccount of the composition dependence of theoretically and practically relevantproperties for various classes of compounds. Since a complete experimentalcharacterization is usually produced only for some selected compositions and temperatures,there has been considerable interest in the design and testing of predictive methodsto extend the database on metallic alloys and compounds. Previous work by ushas been devoted to the application of abinitio calculation methods in producing, systematizing and interpreting newinformation to characterize stable and metastable intermetallic phases (IPs) ofthe Cu-In, Cu-Sn, Ni-In and Ni-Sn systems [1,2]; these being systems ofpotentially interest in connection to lead-free soldering applications. Adatabase including information such as lattice-parameters, cell volume, bulkmodulus and other equation-of-state (EOS) parameters, the energy of formationfrom the elements and the electronic structure have been produced ab initio for relevant IPs of thesesystems. The present work goes one step forward in this line of research byfocusing on the eta phase of the ternary Cu-In-Sn compound. Considerableeffort has been devoted to the characterization of this phase, since it is one of the technologically relevantphases detected at the joint in diffusion couples [3]. The eta phase is acommon equilibrium phase of both the Cu?In (Cu2In of unknownstructure) and Cu?Sn (Cu6Sn5-mC44) binary subsystems ofthe Cu?In?Sn system. The Cu2In and Cu6Sn5 phases have been proposedto form a continuous solid solution in the ternary phase diagram between 186 °Cand 383°C, although no further details are given about the ternary etaphase [4]. Moreover, it was reported that most of theternary IPs occurring at the interconnection zone in Cu/In?Sn/Cu joints arethose formed by incorporating In or Sn to the binary compounds stable in thesubsystems Cu?Sn and Cu?In, respectively [3]. Based on these facts, in thepresent work, we are interested in considering theeffects of incorporating In atoms into the known eta structure of the Cu-Sn intermetallic, viz., (mC44) Cu6Sn5-typephase. The purpose of the work is, in the first place, to establish theenergetically favorable way in which In atoms can replace the Sn atoms in thebinary compound. To this aim we use abinitio projected augmented waves (PAW) calculations using the VASP code tostudy the energy of formation and cohesive energy of the compounds generated byprogressively filling up with In the sublattices originally occupied by Snatoms in the (mC44) Cu6Sn5 phase. In the second place, weaim at studying the effects of the In concentration upon the structural and EOSparameters of the Cu6 (Sn,In)5 phase. The compositiondependence of these calculated properties will be compared with theexperimental data available and with previous theoretical results from theliterature. Finally, we aim at interpreting the theoretical trends byestablishing the composition dependence of the electronic structure anddiscussing that in the light of current theories of p-d bonded intermetallicphases.