Transport of Substitutional Impurities in Noble Metals

The heats o f transport o f several substitutional impurities (such as Sb, Sn, In, Ag, N i and Co) in copper and silver are discussed in terms o f atom ic quantities. They are considered as consisting of essentially two parts. The first one, the so-called intrinsic heat o f transport, can be derived from the electrostatic potential generated by the im purity at the site o f a normal lattice atom in excess over the potential o f the host lattice. This interpretation is compatible with the thermo­ dynamic definition o f the heat o f transport. The calculations were carried out for fee lattices but, in principle, m ay be easily extended to other alloy structures. The second part, calculated by Gerl, is due to the electronic scattering potential o f the impurities. From comparison o f theore­ tical and observed data o f heats o f transport one finds the agreement to be very good. This is taken to be an indication o f the valid ity o f the theoretical models used and o f the vacancy mech­ anism as the dominating mass transport mechanism in these system s, not only in a uniform temperature field but also in a temperature gradient.