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Title: Nonaffine displacements in crystalline solids in the harmonic limit
Authors: Ganguly, Saswati
Sengupta, Surajit
Sollich, Peter
Rao, Madan
Keywords: Elasticity
amorphous solids
General theory
Issue Date: Apr-2013
Publisher: American Physical Society
Citation: Physical Review E, 2013, Vol.87, p042801
Abstract: A systematic coarse graining of microscopic atomic displacements generates a local elastic deformation tensor D as well as a positive definite scalar χ measuring nonaffinity, i.e., the extent to which the displacements are not representable as affine deformations of a reference crystal. We perform an exact calculation of the statistics of χ and D and their spatial correlations for solids at low temperatures, within a harmonic approximation and in one and two dimensions. We obtain the joint distribution P(χ,D) and the two-point spatial correlation functions for χ and D. We show that nonaffine and affine deformations are coupled even in a harmonic solid, with a strength that depends on the size of the coarse-graining volume Ω and dimensionality. As a corollary to our work, we identify the field hχ conjugate to χ and show that this field may be tuned to produce a transition to a state where the ensemble average <χ> and the correlation length of χ diverge. Our work should be useful as a template for understanding nonaffine displacements in realistic systems with or without disorder and as a means for developing computational tools for studying the effects of nonaffine displacements in melting, plastic flow, and the glass transition.
Description: Open Access.
ISSN: 1539-3755
1550-2376 (Online)
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Copyright: 2013 American Physical Society
Appears in Collections:Research Papers (TP)

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