Cohesive Properties of Cu-X and Ni-X (In, Sn) Intermetallics: Ab Initio Systematics, Correlations and "Universality" Features

D. BERTOLDI; S.B. RAMOS; N. V. GONZÁLEZ LEMUS; A. FERNÁNDEZ GUILLERMET

JOURNAL OF PHASE EQUILIBRIA AND DIFFUSION

SPRINGER

Lugar: Berlin; Año: 2017 vol. 38 p. 257 - 267

1547-7037

This paperreports an analysis of the systematics of cohesive properties andequation-of-state parameters for a large number of stable, metastable andhypothetical binary MeaXb type phases formed by Me = Cu, Niwith X = In, Sn. To this aim, an ab initio database previously developed by theauthors using spin polarized density-functional-theory calculations, using theVASP code, is adopted. The work involves the volume (V0),Wigner-Seitz radius, bulk modulus (B0) and cohesive energy (Ecoh)of the phases. At the outset of the paper it is shown that these properties canbe studied as functions of the average group number (AGN), i.e., the weightedaverage of the number of valence electrons involved in the VASP calculations.Moreover, the cohesive energy density (CED), defined as Ecoh/V0,is shown to correlate very well with the AGN variable and with B0.These striking regularities are given two complementary interpretations. First,a general microscopic picture of the variations of cohesion is developed bystudying the evolution of the contributions of the d- and p-electrons to theirelectronic density of states. In this way the effects of the hybridization ofd- and p electrons, and the filling up of bonding and anti-bonding states ishighlighted. Next, a thermodynamic analysis based on the classical approachdeveloped by Rose, Ferrante, Smith and collaborators is performed. It isconcluded that the correlation involving CED and B0 is a manifestation of asignificant degree of "universality" in the variation of the cohesiveproperties with the Wigner-Seitz radius of these compounds.