Positron annihilation of molten binary alloys containing transition metal or noble metal

The angular distribution of positron annihilation N(theta) has been measured for molten binary alloys containing transition metal or noble metal (i.e., molten Fe-Ge, Ni-Ge, Ni-In, Ag-Ge and Au-Ge alloys) at temperatures near the liquidus. The experimental results for molten Fe-Ge, Ni-Ge and Ni-In alloys showed that the broad component of N(theta) arising from annihilation with d-electrons hardly increased even for the concentration of 37 at%Fe(Fe37Ge63) or 33 at%Ni(Ni33Ge67), and only a little increased for the concentration of 50 at%Ni(Ni50Ge50 and Ni50In50). On the other hand, for molten Ag-Ge and Au-Ge alloys, the broad component increased rapidly and monotonously with increasing concentration of Ag or Au. These results correspond well with the feature of ionic structure obtained from X-ray diffraction for molten Ni-Ge and Ag-Ge alloys, and also with the results of XPS measurements for amorphous Fe-Ge, Ni-Ge, Ag-Ge and Au-Ge alloys. The difference in the concentration dependence of N(theta) between molten binary alloys containing transition metal and those containing noble metal may be ascribed to the difference in the ionic structure and the extension of d-wave function in these molten alloys. (author)