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Temperature effects on atomic pair distribution functions of melts
1Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland 21218, USA.
The Journal of Chemical Physics
|February 18, 2014
Summary
This study reveals that the apparent shift in metallic liquid pair distribution functions with temperature is due to peak asymmetry, not just thermal expansion. Covalent liquids show an opposite trend, linked to bond directionality.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Computational Chemistry
Background:
- The temperature-dependent behavior of liquid structures, particularly metallic liquids, is complex and not fully understood.
- Previous studies reported anomalous peak shifts in pair distribution functions (PDFs) of metallic liquids with increasing temperature.
Purpose of the Study:
- To investigate the temperature-dependent evolution of the first peak in PDFs of liquids using molecular dynamics simulations.
- To elucidate the underlying mechanisms causing the observed peak shifts, especially the anomalous behavior in metallic liquids.
Main Methods:
- Employed molecular dynamics (MD) simulations to model liquid systems.
- Conducted constant-volume simulations to isolate the effects of temperature on peak shape and position, excluding thermal expansion.
- Analyzed the asymmetry of the first peak in the pair distribution functions.
Main Results:
- For metallic liquids, the first peak in the PDF shifts left (shorter distances) with increasing temperature.
- This apparent shift is attributed to increasing peak asymmetry caused by anharmonic interatomic potentials, leading to atomic spreading.
- Melts of covalent materials exhibit an opposite peak shift trend, linked to the directional nature of their interatomic bonds.
Conclusions:
- The anomalous peak shift in metallic liquids is primarily an artifact of peak asymmetry, not solely due to thermal expansion or changes in local ordering.
- The anharmonicity of interatomic potentials plays a crucial role in the temperature-dependent structural evolution of metallic liquids.
- Bond directionality is a key factor influencing the structural response to temperature changes in covalent liquids.
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