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SUMMARY:Hard sphere crystal growth - Dr Michiel Hermes (University of Utre
 cht)
DTSTART:20110527T110000Z
DTEND:20110527T120000Z
UID:TALK31122@talks.cam.ac.uk
CONTACT:Dr Mark Miller
DESCRIPTION:We have recently confirmed that hard sphere nucleation can be 
 well described by equilibrium techniques.  We now show that while nucleati
 on can be described by quasi equilibrium techniques\, the subsequent cryst
 al growth cannot.  Using both computer simulations and experiments we show
  that when a single hard sphere nucleus grows out many twinning defects fo
 rm.  These twinning defects have no chance to anneal out because the cryst
 al keeps growing.  This results in a defected nucleus consisting of many d
 ifferently oriented domains.  We observe a large variation in the number a
 nd size of the\ncrystalline domains. We find that this is caused by the st
 ructure of the critical nucleus: a mostly fcc nucleus results in many smal
 l domains while a more randomly stacked nucleus results in much larger dom
 ains.  We subsequently calculate the structure factors of growing nuclei a
 nd analyze these in the same manner as in light scattering experiments. We
  find that the multi-domain structure of these nuclei causes a significant
  broadening of the peaks. This results in over counting the number of nucl
 ei and an overestimation of the nucleation rate at low super-saturation.  
 This might solve the longstanding discrepancy between nucleation rates obt
 ained using\nexperiments and those obtained using computer simulations.
LOCATION:Unilever Lecture Theatre\, Department of Chemistry
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