Th. Halm

Structure of molten copper-germanium alloys

Abstract Copper–germanium alloys in liquid state at 1373 K have been investigated. Non-linear behaviour of the structure-sensitive parameters and electrical resistivity of the alloys versus concentration have been observed. Close relation between the crystal structure and the local ordering in molten Cu–Ge alloys has been found. The inhomogeneous structure of the liquid Cu–Ge alloys at a microscopic level was established. Melts are shown to contain clusters from pure components and clusters with composition corresponding to that of the intermetallic compound Cu 3 Ge existing in the solid phase.

Short-range order in amorphous germanium-tellurium alloys

Abstract The atomic structure of Te-rich amorphous germanium tellurides has been investigated experimentally with high-energy synchrotron radiation and modeled by means of the reverse Monte Carlo technique. Total and partial structure factors and pair correlation functions were simulated. It is shown that the structure of Ge20Te80 and Ge15Te85 glasses can be described by GeTe4 tetrahedra as structural units which are bridged by Te–Te bonds.

The structure of liquid GaIn alloys

Abstract Using X-ray diffraction, the structure factors of molten GaIn alloys were determined as a function of composition at 5 K above the liquidus and at a constant 443 K. The nearest neighbour distances and coordination numbers, obtained from the pair correlation functions, are given. Both structure factors and pair correlation functions could be well reproduced by a micro-inhomogeneous model, proposed by Iljinskij.

Short-range and medium-range order in molten Ga–Tl alloys

Abstract Molten alloys of Ga–Tl were investigated by neutron small- and wide-angle scattering around the miscibility gap which occurs in the liquid state of this binary system. For the alloy containing 40 at.% Tl (the critical composition) and these of 5 at.%Tl less and more than that of the critical composition, an increase of the small-angle scattering intensity was observed as the temperature is decreased and approaches the temperature at the binodal curve, whereas the wide-angle scattering data show no temperature-dependent behaviour in the considered temperature-range. The Ornstein–Zernike formalism was applied to the small-angle scattering data and values for the critical-point exponents ν and γ were estimated. The latter are in good agreement with theoretical values and with results published for other demixing systems.