Volume effects in the intermetallic compounds formed by Ca, Sr, Ba, Eu, and Yb with other elements

The intermediate phases present in 100 A-B binary systems (A=C, Sr, Ba, Eu, Yb; B=Mg, Pd, Pt, Cu, Ag, Au, Zn, Cd, Hg, Al, Ga, In, Tl, Si, Ge, Sn, Pb, As, Sb, Bi) always show volume contractions as regards the linear Zen-like trend. These volume effects are described by the equation V=xVB0+(1-x)VA0-(n+1)(n+2)xn(1-x) mod chi A- chi B mod , where V is the volume per atom for a given phase, VA0 and VBO are the elemental atomic volumes of the components, x is the atomic percentage of B, n is a parameter related to the composition of the phase with the highest contraction value and chi is a charge transfer atomic parameter. The chi values for the 25 considered elements, determined by an iterative fitting process of the experimental data, correlate with Pauling's electronegativity. The atomic volume of about 440 intermetallic compounds have been calculated with an average variance of 2.5% (0.7 AA3/atom). The present empirical prediction confirms the importance of the charge transfer mechanism on the volume effects observed in the intermetallic compounds of electropositive elements.