Dresden 2003 – scientific programme
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M: Metallphysik
M 15: Symposium: Phasenumwandlungen in Schmelzen V
M 15.1: Talk
Tuesday, March 25, 2003, 10:15–10:30, IFW A
Structural relaxation and atomic diffusion in Ni- based alloys — •Suresh Mavila Chathoth1, Andreas Meyer1, Winfried Petry1, and Helmut Schober2 — 1Physik Department E13, Technische Universität München — 2Institut Laue-Langevin, Grenoble
We use incoherent inelastic neutron scattering to study microscopic dynamics in Ni, NiP, PdNiP and PdNiCuP melts. As compared to simple liquids, these melts are characterized by a dense packing of hard spheres with a packing fraction above 0.5. The intermediate scattering function exhibits a structural relaxation that shows stretching in time. The mode coupling theory of viscous liquids gives a consistent description of the dynamics that governs the mass transport. In contrast to simple metallic liquids, the atomic transport in dense Ni based liquids is characterized by a drastic slowing down of dynamics on cooling and a q−2 dependence of the mean relaxation time at intermediate q as a result of a highly collective transport mechanism. Whereas the undercooling capabilities and the stretching exponent of the structural relaxation depend on the alloy composition the Ni self diffusion coefficient is fairly independent on mixing. This indicates that the diffusion mechanism in hard-sphere like liquids is controled by the packing fraction.