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SUMMARY:Overcoming old barriers in the thermally-­activated glide of disl
 ocations
DTSTART:20130924T131500
DTEND:20130924T141500
DTSTAMP:20260513T184707Z
UID:19e5204fd170bb1e42d32473c9d53eb3946052c6b3de42baeee0bff0
CATEGORIES:Conferences - Seminars
DESCRIPTION:David Rodney\, Institut Lumière Matière\, University of Lyon
 \, France\nBio : David Rodney is a Professor of Physics at the University 
 of Lyon. After a PhD in 1999 working between CEA Saclay and Brown Universi
 ty and a post-doc at ONERA Châtillon in 2000-2001\, he became an associat
 e Professor at Grenoble Institute of Technology in 2001 and moved to Lyon 
 in 2013. He was also a visiting scientist at M.I.T. in 2008-2009. He has c
 o-authored more than 60 papers in the field of the multiscale modeling of 
 deformation in materials including crystalline metals\, amorphous glasses 
 and fibrous materials. Since 2012\, he serves as associate Editor for Acta
  Materialia.\nAbstract : Although  thermally-­‐activated  plasticity
   has  been  studied  for  over  50  years\,  vast  aspects  of
   this process   remain   unclear\,   in  particular   regarding
    modeling.   Reasons   range   from  limitations   in continu
 um  modeling  to  include  atomistic  effects\,  difficulties  in 
  developing  realistic  potentials\, interplay between complex processes
 \, such as collective  effects\, dynamical effects\, cross-­‐slip\,  
 … In this seminar\, we will present recent progresses made in the modeli
 ng of probably the best-­‐known dislocation  subjected  to  thermall
 y-­‐activated  glide\,  the  screw  dislocation  in  body-­‐ce
 ntered  cubic crystals.   We  will  show   that  a  static   ap
 proach\,   combining   saddle-­‐point   search   methods   (t
 he Activation-­‐Relaxation  Technique and Nudged Elastic Band method) 
 to identify energy pathways and the Transition State Theory (TST) to predi
 ct kinetics\, allows understanding and modeling accurately the   disloca
 tion   thermally-­‐activated   glide.   Our   approach   make
 s   use  of  a  line   tension   model parameterized on atomistic
  simulations\, which can predict dislocation kinetics at high temperatures
  in the classical regime. At low temperatures\, we will show that the well
 -­‐known fact that atomistic calculations overestimate the Peierls stre
 ss compared to experiments is due to the zero-­‐point energy motion  
  of  atoms\,   which   helps   dislocation   glide   at   low
    temperatures   compared   to   classical calculations and had n
 ot been previously accounted for in atomistic simulations\, as reported re
 cently in Proville\, Rodney\, Marinica\, Nature Materials\, doi: 10.1038/n
 mat3401 (2012).
LOCATION:GC B3 31 http://plan.epfl.ch/?room=GCB331
STATUS:CONFIRMED
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