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SUMMARY:Diffraction of noble gases from surfaces: A challenge for theoreti
 cians - Cristina Díaz\, Department of Chemistry\, Universidad Autónoma d
 e Madrid\, Spain
DTSTART:20170427T150000Z
DTEND:20170427T160000Z
UID:TALK71129@talks.cam.ac.uk
CONTACT:Stephen Walley
DESCRIPTION:The diffraction of noble gases is largely used in surface scie
 nce as a nondestructive analytical tool\, to investigate\, for example\, s
 urfaces morphology\, surface phonons or the dynamics of adsorbate/surface 
 systems [1\,2\,3]. However\, in order to extract the maximum amount of inf
 ormation from experimental diffraction spectra\, a detailed comparison wit
 h theoretical simulations is often desirable. The periodic lattice structu
 re of a noble-gas atom/surface system could be\, in principle\, well descr
 ibed by density functional theory (DFT) with periodic boundary conditions.
  However\, standard DFT functionals do not include\, per se\, the effect o
 f the van der Waals (vdW) forces\, which are expected to be the main respo
 nsible forces driving the interaction of noble-gas atoms with surfaces. In
  the early 2000s\, it was suggested\, for example\, that standard DFT coul
 d provide an appropriate description of scattering of Ne and He from a met
 al surface\, due to the small interatomic distances at the classical turni
 ng points [4]. However\, this hypothesis was never tested through a direct
  comparison with experimental diffraction spectra.\nWe have carried out th
 is test using as benchmark systems Ne/Ru(0001) [5]. We have performed a de
 tailed theoretical study of diffraction of Ne/Ru(0001) using standard DFT 
 and state-of-the-art DFT with explicit inclusion of vdW effects. Our study
  reveals that taking into account vdW forces is essential to accurately re
 produce experimental results. Furthermore\, our results also suggest that 
 only methods that go beyond pairwise-based corrections are able to accurat
 ely describe diffraction of noble-gas atoms from surfaces. On the other ha
 nd\, despite the promising results obtained for Ne\, He diffraction remain
 s a challenge. \n\n\n\n1- D. Farías\, and K. H. Rieder\, Rep. Prog. Phys.
  61\, 1575 (1998)\n\n2- A. P. Graham\, Surf. Sci. Rep. 49\, 115 (2003)\n\n
 3- G. Alexandrowicz\, A. P. Jardine\, P. Fouquet\, S. Dworski\, W. Allison
 \, and J. Ellis\, Science 304\, 1790 (2004)\n\n4- J. L. F. DaSilca\, C. St
 ampfl\, and M. Scheffler\, Phys. Rev. Lett. 90\, 066104 (2003)\n\n5- M. de
 l Cueto\, A. S. Muzas\, G. Füchsel\, F. Gatti\, F. Martín\, and C. Díaz
 \, Phys\, Rev\, B 93\, 060301(R) (2016)\n
LOCATION:Mott Seminar Room\, Cavendish Laboratory
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