Dresden 2011 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 8: Liquid and Amorphous Metals II

MM 8.2: Talk

Monday, March 14, 2011, 14:45–15:00, IFW D

Thermophysical properties and medium-range order of liquid Ni-Si alloys — Yongjun Lü and •Peter Entel — Faculty of Physics and Center for Nanointegration, CeNIDE, University of Duisburg-Essen, 47048 Duisburg, Germany

The thermophysical properties of liquid Ni-Si alloys as a function of silicon concentration are investigated using molecular dynamics simulations. The temperature dependent enthalpy and density indicate the occurrence of crystallization in Ni-5%Si and Ni-10%Si and glass transitions for 20% and 25%. With the Si concentration increasing from 5 to 25%, the self-diffusivities decrease and viscosities increase with more non-Arrhenius temperature dependences in the low-temperature region, suggesting fragile characteristics of these alloys. Moreover, a shoulder peak emerges between the first and second peak in all radial distribution functions before crystallization or glass transition. Positions of shoulder, second and third peaks relative to the nearest neighbor peak are consistent with a global packing model [1], showing the incompact local translational symmetry. The atomic arrangement prefers a special bond angle distribution and displays orientational order. Therefore, the medium-range order of liquid Ni-Si can be described as a combination of local translational and orientational orders. This local packing structure becomes more compact with addition of more Si atoms, suppressing the formation of crystalline order.

[1] X. J. Liu et al. Phys. Rev. Lett. 105, 155501(2010)