Journal
ACTA MATERIALIA
Volume 141, Issue -, Pages 75-82Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.actamat.2017.09.014
Keywords
Metallic glass; Equation of state; Density scaling; Structure factor
Funding
- National Natural Science Foundation of China [11474126, 51701180]
- Canada Research Chair program
- Zhejiang Provincial Natural Science Foundation of China [LQ16E010003]
- Natural Science and Engineering Research Council of Canada (NSERC)
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The existence of a universal power law relating the position of the first sharp diffraction peak (q, FSDP) to the density (p or the volume V) with a constant exponent <3 has been debated in the last decade. A constant dimensionality is important because it reflects the fractal topology of the glass structures. In this study, the validity of the Ehrenfest equation applied to multi-component metallic glasses is examined using first-principles molecular dynamics calculations. The results show that the Ehrenfest coefficient depends on the local structures of the glasses and is not a constant for all glasses. Moreover, since the diffraction pattern is determined by the scattering between atom pairs, in a multi-component glass, the X-ray diffraction FSDP is only sensitive to the heavy atoms, and the observed P-q relationship does not necessary correspond to the P-V equation of state of the bulk material and is not always a suitable indicator for monitoring structural phase transitions or volume changes. On the other hand, for suitable systems, neutron diffraction is a reliable method to determine the structural features of both heavy and light atoms. In this study, the simulated neutron diffraction patterns of Ca72.7Al27.3 metallic glasses show a clear splitting of the FSDP at the pressure where the pressure-induced polyamorphism transition occurs. From the presented results, there is no justification for expecting the existence of a universal power scaling law with a constant exponent for all glasses. (C) 2017 Published by Elsevier Ltd on behalf of Acta Materialia Inc.
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