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SUMMARY:Molecular Origin of K13 Revisited - Yokoyama\, H (Kent State Unive
 rsity)
DTSTART:20130108T153000Z
DTEND:20130108T163000Z
UID:TALK42319@talks.cam.ac.uk
CONTACT:Mustapha Amrani
DESCRIPTION:Expanding a distortion free energy in terms of spatial gradien
 ts of density is a standard approach to construct an elastic theory of con
 densed matter. When applied to nematic liquid crystals\, this so-called gr
 adient expansion leads to the celebrated Frank theory that serves as the s
 ound basis on which to analyze the response of nematic liquid crystals to 
 electric fields and boundary constraints. The success of the theory has be
 en thoroughly proven except the anomalous surface contribution associated 
 with K13 (splay-bend elasticity). The K13 term involves a gradient of the 
 nematic director normal to the boundary\, and hence the straightforward mi
 nimization of free energy under a given boundary condition becomes mathema
 tically ill-posed\, running into various unphysical behaviors.\n\nMore tha
 n a decade ago\, I showed (at least I think I showed) that K13 is an artif
 act of gradient expansion as applied to a nonlocal interaction free energy
  by way of the density functional theory. When consistently done\, the gra
 dient expansion always results in K13=0 eliminating all the lingering prob
 lems that K13 has created.\n\nThe purpose of this talk is to revisit this 
 issue. Close look at the K13 issue at the molecular level not only solves 
 its own problem but also gives us a chance to shed new light on such funda
 mental structural characteristics of liquid crystals as chirality\, flexoe
 lectricity\, and more. \n\n
LOCATION:Seminar Room 1\, Newton Institute
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