BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Talks.cam//talks.cam.ac.uk//
X-WR-CALNAME:Talks.cam
BEGIN:VEVENT
SUMMARY:Water clusters\, ice and liquid: Improving ab initio energetics - 
 Mike Gillan (University College\, London)
DTSTART:20120314T110000Z
DTEND:20120314T114000Z
UID:TALK36268@talks.cam.ac.uk
CONTACT:Dr. Mike Towler
DESCRIPTION:Water has probably been studied more comprehensively than any 
 other substance\, but its energetics remains surprisingly elusive. The pro
 perties of water\nclusters\, ice structures and the bulk liquid are poorly
  reproduced by conventional density functional theory (DFT)\, for reasons 
 that are still controversial. I will summarise some new approaches that we
  are pursuing at UCL\nin collaboration with colleagues in Cambridge and Br
 istol\, focusing particularly on our recent work with quantum Monte Carlo 
 (QMC) [1]\, but emphasising also the ideas of Gaussian Approximation Poten
 tials [2]. I will \nshow that QMC is much more accurate than DFT for the e
 nergetics of clusters and ice structures\, and that it can also supply ene
 rgy benchmarks for statistical \nsamples of configurations of the bulk liq
 uid. We are using the benchmarks to  analyse the source of errors in DFT a
 pproximations and to quantify the accuracy\nof GAP corrections to DFT. It 
 is becoming clear from this work that conventional DFTs struggle to descri
 be water systems correctly because they misrepresent the subtle balance be
 tween 2-body and beyond-2-body parts of the energy.\n\n[1] M. J. Gillan\, 
 M. D. Towler and D. Alfe\, “Petascale computing opens new \nvistas for q
 uantum Monte Carlo”\, Scientific Highlight\, Psi-k Newsletter No. \n103\
 , February 2011.\n\n[2] A. P. Bartok\, M. C. Payne\, R. Kondor and G. Csan
 yi\, “Gaussian Approximation Potentials: The accuracy of quantum mechani
 cs without the electrons”\, Phys. \nRev. Lett.\, 140\, 136403 (2010).\n
LOCATION:TCM Seminar Room\, Cavendish Laboratory
END:VEVENT
END:VCALENDAR