Nonmetal-metal transition in liquid Cu-based alloys

Electrical conductivity sigma (T) and thermo-e.m.f. S(T) measurements were performed for ternary Cu-based chalcogenides in a wide temperature range. A concentration range of the semiconductor-metal transition has been determi ned. A radical alteration in the electron spectrum occurs in the region of x = 0.6-0.8, namely, a semiconductor-metal transition takes place. Complete metallization of alloys takes place with temperature increasing. Further h eating is accompanied by electrical conductivity decreasing followed by fin al exponential electrical conductivity dependence with seeming "negative" a ctivation energy, while thermopower increases without changing a sign. This process is accompanied by an increase of a free electrons concentration. A t the same time, at higher temperatures when the alloy's density decreases, localization of the wave functions of electrons on separated atoms or atom s groups caused by density fluctuations, occurs. For alloys with Se content , the electrical conductivity decreasing caused by thermal expansion, could be intensified at the expense of molecular units formation. A simultaneous density decreasing causes an appearance of small dynamic groups like Se-2, Se-3, Se-6. While similar molecular complexes appear, a very inhomogeneous in a structural and energy sense system in being formed. Peculiarities of the reverse metal-semiconductor transition were studied.