RAMOS susana Beatriz
congresos y reuniones científicas
Ab-initio study of Cu-In and Cu-Sn intermetallic phases. Calculation of energy parameters involved in the thermodynamic assessment of the Cu-In-Sn system using sublattice models
Buenos Aires
Workshop; At the Frontiers of Condensed Matter Physics V; 2010
Institución organizadora:
Contro Atómico Constituyentes
The In-48at.%Sn eutectic alloy is an attractive candidate for the development of Pb-free solders within the diffusion soldering method. In order to understand the phase formation between the soldering alloy and the Cu substrate, the knowledge of the physico-chemical properties of the formed intermetallic phases (IPs) and the phase equilibrium properties of the Cu-In-Sn system are of great importance. Previous attempts to investigate the phase stability of the IPs of the Cu-In-Sn system were based on combining the experimental information available, with thermodynamic models for the Gibbs free energy of the ternary and binaries phases. In this way using methods likethe CALPHAD method (”Calculation of Phase Diagrams”) it is possible to get useful predictions for the phase relations on the ternary field, starting from information of the binary subsystems. Extensions of the binary phases to the ternary field can be modeled by the Compound Energy Formalism, in which varying amounts of the third element are added substitutionally to the binary phase. Certain IPs of the Cu-In-Sn system can be treated with models of the type (Cu)a(In,Sn)b, while others non-stoiquiometric Cu-In and Cu-Sn binary phases, with models of the type (Cu)a(In,Sn)b(In)c o (Cu)a(In,Sn)b(Sn)c, respectively. In this work we perform ab-initio calculations using the Vasp Code to determine the energy parameters involved in the application of CEF to various IPs of the Cu-In-Sn system. We use the the projector augmented wave potentials (PAW) and the exchange-correlation functions of Perdew and Wang in the generalized gradient approximation. We study the end-member compounds involved in the CEF treatment of the ternary phases generated by adding In to the binaries epsilon-Cu3Sn (oP8) and xi-Cu10Sn3 (hP26), and adding Sn to the CuIn2 phase (tI12). This work extends a recent research performed for the end members associated to delta-Cu7In3 (aP40), eta´-Cu2In (hP6) and eta´-Cu6Sn5 (mC44) phases. All these results are considered to establish trends in the relative stability and thermodynamic properties of the IPs of the Cu-In and Cu-Sn subsystems. We critically compare the calculated formation energies for the CEFs compounds with data previously obtained by phenomenological Cu-In-Sn CALPHAD analysis.