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CATEGORIES:Biological and Statistical Physics discussion grou
p (BSDG)
SUMMARY:Lattice dynamics and vibrational excitations in ra
ndom networks and disordered crystals - Alessio Za
ccone (Cavendish Laboratory\, BSS)
DTSTART;TZID=Europe/London:20160526T120000
DTEND;TZID=Europe/London:20160526T130000
UID:TALK66019AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/66019
DESCRIPTION:Random networks (e.g. actin networks) and disorder
ed condensed matter (e.g. glasses) cannot be descr
ibed by standard lattice dynamics concepts\, due t
o the lack of periodicity of the lattice. We contr
ibuted to develop a formalism which extends lattic
e dynamics to aperiodic solids\, including glasses
(e.g. metallic glasses)\, by building on the key
concept of nonaffine displacements. Atoms in a per
fect centro-symmetric crystals are local centers o
f inversion symmetry. In disordered and defective
lattices\, this is no longer true. This simple sym
metry consideration has huge implications for the
dynamics: under an applied deformation field\, for
ces received by a test atom from its neighbours ca
nnot cancel by symmetry in the displaced position
prescribed by the deformation tensor. Hence\, the
atomic displacement cannot be a simple affine tran
sformation\, but necessarily implies extra displac
ements necessary to keep mechanical equilibrium wh
ich are called non-affine displacements [1]. Imple
menting this basic fact in lattice dynamics leads
to a number of predictions which can explain vario
us anomalous features in: the elastic constants [2
]\, the glass-liquid transition [3]\, the vibratio
nal density of states and low-T specific heat of g
lasses [4]\, the non-linear deformation and yieldi
ng of glasses [5].\n\n[1] A. Zaccone & E. Scossa-R
omano\, Phys. Rev. B 83\, 184205 (2011). [2] A. Za
ccone & E.M. Terentjev\, J. Appl. Phys. 115\, 0335
10 (2014). [3] A. Zaccone & E. Terentjev\, Phys. R
ev. Lett. 110\, 178002 (2013). [4] R. Milkus & A.
Zaccone\, Phys. Rev. B 93\, 094204 (2016). [5] A.
Zaccone\, P. Schall\, E. M. Terentjev\, Phys. Rev.
B 90\, 140203(R) (2014).
LOCATION:TCM Seminar room\, 530 Mott building
CONTACT:Salvatore Tesoro
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