Ab initio study of thermophysical and mechanical properties of Ni-X (X=In,Sn) intermetallic compounds

D. BERTOLDI; S.B. RAMOS; A. FERNÁNDEZ GUILLERMET

La Plata

Workshop; IX Novel Methods for Electronic Structure Calculations; 2021

Facultad de Ciencias Exactas - Universidad Nacional de La Plata

There is long-standing interest in the study of intermetallic phases (IPs) of the Ni-In and Ni-Sn systems in relation to the In-Sn alloys and their use in lead free micro-soldering processes, considering Ni as the contact material. In this work we investigate by ab initio density functional theory calculations the cohesive, elastic and thermodynamic properties of several intermetallic phases (IP) of the Ni-In and Ni-Sn systems. In particular, we are interested in extending the ab initio database previously developed by the present authors at zero-kelvin to include finite temperature properties. To this end we have performed density functional theory calculations in combination with the quasi-harmonic approximation (QHA) to predict the vibrational density of states, the frequency moments and related Debye temperatures, the Gibbs energy and the heat capacities. Specifically, the T = 0 K energy-volume relations determined by VASP were combined with phonon calculation using the PHONOPY code to develop a QHA account of the vibrational thermal properties of various Ni-In and Ni-Sn IPs. In the present work the electronic contribution to the heat capacities and other thermal properties of the low temperature Ni3X (X =In,Sn) hP8 phase stable, the high pressure cP4 phase and the elements Ni, In and Sn is determined. Moreover, the Gibbs energy of the Ni3X (X=In,Sn) in the hP8 and cP4 phases is determined, and the relative stabilities of these phases as a function of pressure is discusses. We also analyze trends on the composition dependence of these properties and compare with available experimental data.