Eur. Phys. J. E (2009) 30: 303-307
https://doi.org/10.1140/epje/i2009-10531-6

Regular Article

Relationship between vibrations and dynamical heterogeneity in a model glass former: Extended soft modes but local relaxation

¹ School of Physics and Astronomy, University of Nottingham, NG7 2RD, Nottingham, UK
² Department of Physics, University of Bath, BA2 7AY, Bath, UK

^* e-mail: d.ashton@bath.ac.uk

Received: 24 November 2008
Revised: 31 July 2009
Accepted: 8 October 2009
Published online: 27 October 2009

Abstract

We study the relation between short-time vibrational modes and long-time relaxational dynamics in a kinetically constrained lattice gas with harmonic interactions between neighbouring particles. We find a correlation between the location of the low- (high-) frequency vibrational modes and regions of high (low) propensity for motion. This is similar to what was observed in continuous force systems, but our interpretation is different: in our case relaxation is due to localised excitations which propagate through the system; these localised excitations act as background disorder for the elastic network, giving rise to anomalous vibrational modes. Our results provide an example whereby a correlation between spatially extended low-frequency modes and high-propensity regions does not imply that relaxational dynamics originates in extended soft modes but rather belies their common origin. We consider other measures of elastic heterogeneity, such as non-affine displacement fields and mode localisation lengths, and discuss implications of our results to interpretations of dynamic heterogeneity more generally.