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SUMMARY:Accelerating linear-scaling DFT:  Differential geometry meets elec
 tronic structure theory - David O'Regan (TCM)
DTSTART:20101117T110000Z
DTEND:20101117T114000Z
UID:TALK21833@talks.cam.ac.uk
CONTACT:Dubois Simon
DESCRIPTION:The use of nonorthogonal functions to support single-particle 
 states is ubiquitous in contemporary density functional theory\, indeed\, 
 it is practically obligatory if one wishes to construct a method for which
  the effort scales with system size. As a result\, it is of increasing imp
 ortance to understand the measures which must be taken to accommodate it. 
 In this talk I will begin by going "back to basics"\, exploring the conseq
 uences of support function nonorthogonality and attempting to shed light o
 n the accompanying notation and terminology so often used by linear-scalin
 g DFT practitioners.\n\nFor many tasks we may wish to change the support f
 unctions during the course of a calculation. For example\, in ONETEP a set
  of nonorthogonal generalised Wannier functions (NGWFs) are optimised to a
 ccurately minimise the total energy\, in DFT+U the nonorthogonal Hubbard p
 rojectors may be made consistent with the NGWFs (projector self-consistenc
 y) or optimised to meet another criterion such as providing a maximal the 
 U tensor\, and in linear-scaling TDDFT one may wish to propagate the suppo
 rt functions in time in order to achieve plane-wave accuracy. I will analy
 se the consequences of support function optimisation in each of these case
 s on geometric grounds and\, on that basis\, demonstrate a first-principle
 s method to improve both the numerical stability and speed of such calcula
 tions.
LOCATION:TCM Seminar Room\, Cavendish Laboratory
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