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Title: Local Structural Fluctuations in a Supercooled Liquid

Abstract

The local structural properties of a supercooled metallic liquid system are examined using molecular dynamics simulations. These local properties include pressure, bulk modulus, shear modulus, volume strain and shear stress. We find two-step changes in the hydrodynamic diameter relating the diffusion to the shear viscosity in the Stokes-Einstein relation. They are closely correlated with the change in behavior of the structural fluctuations and the radial distribution function. We relate these changes with freezing of local shear and density fluctuations.

Authors:
 [1];  [1];  [1];  [1]
  1. ORNL
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
931923
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Conference
Resource Relation:
Conference: 2006 TMS Annual Meeting and Exhibition, San Antonio, TX, USA, 20060312, 20060316
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; CRYOGENIC FLUIDS; MORPHOLOGY; MOLECULAR DYNAMICS METHOD; FLUCTUATIONS; HYDRODYNAMICS; VISCOSITY

Citation Formats

Aga, Rachel S, Morris, James R, Levashov, Valentin A, and Egami, Takeshi. Local Structural Fluctuations in a Supercooled Liquid. United States: N. p., 2006. Web.
Aga, Rachel S, Morris, James R, Levashov, Valentin A, & Egami, Takeshi. Local Structural Fluctuations in a Supercooled Liquid. United States.
Aga, Rachel S, Morris, James R, Levashov, Valentin A, and Egami, Takeshi. Sun . "Local Structural Fluctuations in a Supercooled Liquid". United States. doi:.
@article{osti_931923,
title = {Local Structural Fluctuations in a Supercooled Liquid},
author = {Aga, Rachel S and Morris, James R and Levashov, Valentin A and Egami, Takeshi},
abstractNote = {The local structural properties of a supercooled metallic liquid system are examined using molecular dynamics simulations. These local properties include pressure, bulk modulus, shear modulus, volume strain and shear stress. We find two-step changes in the hydrodynamic diameter relating the diffusion to the shear viscosity in the Stokes-Einstein relation. They are closely correlated with the change in behavior of the structural fluctuations and the radial distribution function. We relate these changes with freezing of local shear and density fluctuations.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}

Conference:
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  • Time-resolved synchrotron measurements were carried out to capture the structure evolution of an electrostatically levitated metallic-glass-forming liquid during free cooling. The experimental data shows a crossover in the liquid structure at ∼1000 K, about 115 K below the melting temperature and 150 K above the crystallization temperature. The structure change is characterized by a dramatic growth in the extended-range order below the crossover temperature. Molecular dynamics simulations have identified that the growth of the extended-range order was due to an increased correlation between solute atoms. These results provide structural evidence for a liquid-to-liquid-phase-transition in the supercooled metallic liquid.
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  • We observed homogeneous nucleation process of supercooled liquid Fe by molecular dynamics simulations. Using bond-orientational order parameters together with Voronoi polyhedron method, we characterized local structure, calculated the volume of Voronoi polyhedra of atoms and identified the structure and density fluctuations. We monitored the formation of nucleus and analyzed its inner structure. The birth and growth of the pre-nucleus and nucleus are accompanied with aggregating and disaggregating processes in the time scale of femtosecond. Only the initial solid-like clusters (ISLC), ranging from 1 to 7 atoms, pop up directly from liquid. The relation between the logarithm of number of clustersmore » and the cluster size was found to be linear for ISLCs and was observed to be parabolic for all solid-like clusters (SLC) due to aggregating and disaggregating effects. The nucleus and pre-nuclei mainly consist of body centered cubic (BCC) and hexagonal close packed atoms, while the BCC atoms tend to be located at the surface. Medium-range structure fluctuations induce the birth of ISLCs, benefit the aggregation of embryos and remarkably promote the nucleation. But density fluctuations contribute little to nucleation. The lifetime of most icosahedral-like atoms (ICO) is shorter than 0.7 ps. No obvious relationship was found between structure/density fluctuations and the appearance of ICO atoms.« less