Surface Activity of sp-Metals in Molten Intermetallic Compounds

The dependence of the surface-layer composition of a molten binary intermetallic compound (IMC) on factors determining electrochemical properties of liquid electrodes in indifferent electrolytes is studied. The segregation of the binary melt components at the interface with vacuum is considered in terms of physical materials technology. The interface state of the molten IMC is described by the Landau–Ginzburg functional for a surface excess of the Gibbs free energy. An examination of the functional shows that a minimum energy at a given temperature and system volume is reached by depositing the component with the lowest surface tension at the plain component's mp on the melt surface. The deposit has the character of a mesophase; therefore, it remains liquid at temperatures much lower than the plain component's mp in the bulk phase. The dilation interactions between atoms near the interface, caused by different atomic volumes of components, favor the deposition of the metal with a higher atomic volume. The calculated change of the surface tension of Ga–Tl IMC as related to plain Ga is close to relevant experimental value obtained on neutral Ga and Ga–Tl electrodes in an indifferent electrolyte.