ELECTRONIC CONTRIBUTION TO THE ENTROPY OF MIXING OF LIQUID TRANSITION METAL BASED ALLOYS

Experimental results on the entropy of mixing of liquid transition metal based alloys FeSi, CoSi and NiSi show that there is an exceptional negative entropy of mixing. We have shown that this effect is due to the electronic contribution of entropy which is proportional to the density of states at the Fermi level. As the transition metal is alloyed with Si, the free valence electrons of Si produce an s-d transfer leading to a filling of the d-band of the transition metal. This leads to a decrease of entropy when alloying due to decrease in density of states at the Fermi level. Our numerical results show good agreement with experiments. We have also been able to ascribe the change in the concentration of Si, for minimum entropy, as due to the difference in the filling and the shape of the d-bands in the pure liquid Fe, Co and Ni metals