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SUMMARY:From molecular symmetry to order parameters - Zhang\, P (Peking Un
 iversity)
DTSTART:20130111T090000Z
DTEND:20130111T094000Z
UID:TALK42390@talks.cam.ac.uk
CONTACT:Mustapha Amrani
DESCRIPTION:We propose a systematic molecular modeling of liquid crystals\
 , the models can be used to depict isotropic\, nematic\, smectic\, columna
 r\, cholesterics and blue phases. The tensor model can be reduced from mol
 ecular model using closure and Taylor expansion\, the vector model can be 
 reduced from tensor or molecular model using axial symmetry assumption. Us
 ing Newton mechanic and virial expansion\, we build a generic molecular mo
 del to describe phase behaviors of rigid molecules of arbitrary shape. The
  system is characterized by a pairwise kernel function. The kernel functio
 n can be simplified by the molecular symmetry. Onsager potential is a lead
 ing order for rod-like molecular using hard core potential\, and Maier-Sau
 pe potential is a good second approximation using Lennard Jones potential.
  The new models including simplified kernel functions are proposed for ben
 t-core molecules and other shape molecules. We also clarify the criteria o
 f choosing order parameters\, both from theoretical aspects and from resul
 ts of experiments and simulations. According to these criteria\, we explai
 n why the eigenvalue of second moment is chosen to describe spatially homo
 geneous phases of rod-like molecules\, and predict the choice of order par
 ameters for bent-core molecules and other molecules of different symmetrie
 s. The rigorous analysis for choosing the order parameter will be given fo
 r Maier-Saupe model of rod-like molecular. \n\n
LOCATION:Seminar Room 1\, Newton Institute
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