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CATEGORIES:Lennard-Jones Centre
SUMMARY:Long-range screening and interatomic forces: from 
 3D to 2D - Miquel Royo\, Institut de Ciència de Ma
 terials de Barcelona
DTSTART;TZID=Europe/London:20220124T143000
DTEND;TZID=Europe/London:20220124T150000
UID:TALK167264AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/167264
DESCRIPTION:The foundation of modern theory of lattice dynamic
 s rests on the separation between short-range and 
 long-range interatomic force constants\, where the
  latter are associated with macroscopic electric f
 ields acting in a neighborhood of the Brillouin zo
 ne center. In three-dimensional (3D) insulators\, 
 the famous dipole-dipole formula was established l
 ong ago by Cochran and Cowley\; the subsequent wor
 k of Pick\, Cohen and Martin provided a formal der
 ivation in the framework of first-principles theor
 y.\nRecently\, we have incorporated higher-order i
 nteractions involving\, e.g.\, dynamical quadrupol
 es\,[1] and demonstrated their role in the accurat
 e interpolation of phonon band structures.[2] In t
 his talk\, I shall retrace an analogous journey in
  the context of two-dimensional (2D) crystals\, by
  presenting a rigorous derivation of the long-rang
 e screening and interatomic forces in 2D.[3] This 
 enables a systematic generalization of the existin
 g formulas [4] to an arbitrary multipolar order. I
 n particular\, I will discuss how to incorporate o
 ut-of-plane dipoles and dynamical quadrupoles in t
 he long-range part of the dynamical matrix\, and h
 ow to achieve an optimal representation of the die
 lectric function. Numerical tests on monolayer BN\
 , SnS2 and BaTiO3 membranes demonstrate a drastic 
 improvement in the description of the long-range e
 lectrostatic interactions\, with comparable benefi
 ts to the quality of the interpolated phonon band 
 structure.[3]\n\n[1] M. Royo and M. Stengel\, Phys
 ical Review X 9\, 021050 (2019).\n\n[2] M. Royo\, 
 K. Hahn and M. Stengel\, Physical Review Letters 1
 25\, 217602 (2020).\n\n[3] M. Royo and M. Stengel\
 , Physical Review X 11\, 041027 (2021).\n\n[4] T. 
 Sohier et al.\, Nano Letters 6\, 3758 (2017).
LOCATION:Venue to be confirmed
CONTACT:Dr M. Simoncelli
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