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SUMMARY:Traveling and resting crystals in crowds of self-propelled particl
 es - Menzel\, A (Heinrich-Heine-Universitt Dsseldorf)
DTSTART:20130624T133000Z
DTEND:20130624T140000Z
UID:TALK45863@talks.cam.ac.uk
CONTACT:Mustapha Amrani
DESCRIPTION:When the density within a crowd of self-propelled particles is
  high enough and when the interactions between these particles are strong 
 enough\, then it is plausible to expect that crystallization will occur. W
 e are interested in the formation and in the behavior of such active cryst
 als that are composed of self-propelled particles. To study this kind of m
 aterials using a field approach\, we combine the classical phase field cry
 stal model by Elder and Grant with the Toner-Tu theory for active media. I
 n this way we obtain an active phase field crystal model. Our approach can
  further be justified from dynamic density functional theory. The active c
 rystals that we identify can be classified into two groups: either the cry
 stal is resting\, meaning that no net density flux is observed\, or it is 
 traveling\, meaning that the lattice peaks collectively migrate into one d
 irection. As a central result we find that a transition from a resting to 
 a traveling crystal can occur at a threshold value of the active drive. Co
 nsequently a variety of different crystalline phases can be identified: re
 sting hexagonal\, traveling hexagonal\, swinging hexagonal\, traveling rho
 mbic\, traveling quadratic\, resting lamellar\, traveling lamellar\, resti
 ng honeycomb\, and traveling honeycomb. Upon quenching from the fluid phas
 e\, the traveling crystals emerge through a coarse-graining process from d
 omains of different directions of collective motion. Qualitatively we also
  studied the impact of additional hydrodynamic interactions between the la
 ttice peaks. Since the properties and response of active crystals can be v
 ery different from their equilibrium counterparts\, the knowledge of\, cla
 ssification of\, and control of the different crystalline states can provi
 de a starting point for the design of new active materials. \n\nCo-author:
  Hartmut Lowen (Heinrich Heine University Dusseldorf\, Germany) \n
LOCATION:Seminar Room 1\, Newton Institute
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