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Pressure-Induced Structural Transformation in Cristobalite Studied by Molecular Dynamic Simulations

Published online by Cambridge University Press:  21 February 2011

Lucas Duffrene  and
John Kjeffer
Lucas Duffrene
Affiliation:
Department of Materials Science & Engineering, University of Illinois, Urbana IL 61801
John Kjeffer
Affiliation:
Department of Materials Science & Engineering, University of Illinois, Urbana IL 61801
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Abstract

The phase transformation between the α- and β-cristobalite modifications of SiO2 were studied using molecular dynamic simulations. The transformation was induced isothermally by control of the pressure within the structure, either through an externally applied constant stress or by changing the simulation box volume. The atomic scale mechanisms of the transformation can best be observed by means of a time-correlation function describing the spatial orientation of the planes containing the Si-O-Si bonds. These planes rotate by 90° over the course of the transition. Both, the bulk modulus, calculated for static structures, as well as the vibrational spectra of the Si-O-Si planes, reflect the softening of acoustic modes in the midst of the transition, which is characteristic of displacive phase transformations. Although the aperiodic shift of atomic positions upon passage of the transformation front could be responsible for a momentary softening of the structure, this is not the only reason, since this behavior persists when maintaining the structure at intermediate densities, which corresponds neither to α-, nor to β- cristobalite.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 398: Symposium C – Thermodynamics and Kinetics of Phase Transformations , 1995 , 451
Copyright
Copyright © Materials Research Society 1998

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References

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