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SUMMARY:Flexoelectricity from first principles - Prof. Cyrus E. Dreyer\, S
 tony Brook University and Flatiron Institute
DTSTART:20190513T131500Z
DTEND:20190513T141500Z
UID:TALK123055@talks.cam.ac.uk
CONTACT:Bartomeu Monserrat
DESCRIPTION:The flexoelectric (FxE) effect\, where polarization is induced
  by a strain gradient\, is universal in all insulators. As devices shrink 
 to the micro and nano scale\, large strain gradients can occur\, and there
 fore the FxE effect can play a significant role in their electrical and me
 chanical properties. Also\, the FxE effect can be exploited for novel devi
 ce design paradigms such as piezoelectric ``meta-materials'' constructed f
 rom nonpiezoelectric constituents\, or mechanical switching of ferroelectr
 ic polarization. One of the crucial limitations to understanding and explo
 iting the FxE effect has been the lack of an efficient first-principles me
 thodology to calculate all of the components of the bulk FxE tensor\; the 
 clamped-ion transverse and shear components in particular are problematic.
  We have developed such a methodology based on density functional perturba
 tion theory to calculate the full bulk\, clamped-ion FxE tensor with unpre
 cedented accuracy and efficiency. In this talk I will review the microscop
 ic aspects of the FxE effect\, describe our computational methodology\, an
 d provide results for some simple systems including cubic perovskite oxide
 s. \n
LOCATION:TCM Seminar Room\, Cavendish Laboratory
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