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E u r o S c i C o n C o n f e r e n c e o n
Chemistry
2018
Chemistry 2018
Journal of Organic & Inorganic Chemistry
ISSN 2472-1123
F e b r u a r y 1 9 - 2 0 , 2 0 1 8
P a r i s , F r a n c e
Page 19
Generally, while dealing with mixed crystals, the crucial issue is to determine
whether the atom substitution is ideally random or due to local clustering/
anti-clustering. In the latter case, the next issue is to estimate the deviation
from random substitution via some relevant order parameter. Raman scattering
is interesting with respect to the raised issues because it probes the force
constant of a chemical bond, which is a local property. As such, it is presumably
sensitive to the local environment of a bond. Moreover, Raman scattering is
conveniently operated at the laboratory scale, being non-destructive, fast, and
relates to the crystal in volume. However, if we refer to the admitted models
for the description of the abundant Raman spectra of the mixed crystals with
cubic structure, worked out at the emergence of such systems in the sixties,
namely the modified-random-element-isodisplacement (MREI) model and
the cluster model, they both fail to account for the natural complexity of the
Raman spectra of most random mixed crystals, not to mention about the non-
random ones. Basically the MREI model falls short of explaining the natural
complexity in question, while the cluster model overestimates it by far. Over
the past decade we have introduced a novel model to discuss the Raman
spectra of the mixed crystals with cubic structure, the so-called percolation
model that seems to apply universally. Moreover, as this model distinguishes
between the vibrations of like bonds depending on whether they vibrate in like
or foreign environment, it offers a possibility to formalize any trend towards
local clustering/anti-clustering (like environment favored/disfavored) via
the Raman intensities. In this communication we provide a comprehensive
overview of the percolation scheme covering various vibrations addressed in
a Raman experiment (the purely-mechanical TO modes as well as the polar LO
and phonon-polariton ones), supported by ab initio calculations.
Biography
Olivier Pagès has completed his PhD in Solid State Physics on
“Study by Raman scattering of the electronic band bending at
the interface between semiconductor compounds” from Uni-
versité Paul Sabatier (Toulouse III, France). He then conducted
Postdoctoral studies at the Birkbeck College (London University,
UK) for 1.5 years on “Dielectric approaches of percolation phe-
nomena occurring in highly complex binary polymeric mixtures
of the insulating-conducting type”. He is presently the Director
of the Laboratoire de Chimie et Physique – Approche Multi-Ech-
elle des Milieux Complexes (LCP-A2MC) de l’Université de Lor-
raine (Nancy-Metz, France). His field of research is concerned
with the introduction of a percolation-based approach for the
very basic understanding of the vibrational properties of the
mixed crystals that can be viewed as the most simple out of
complicated systems. He has published more than 65 papers
in reputed journals on the subject.
The percolation scheme for the very basic understanding of the Raman
spectra of mixed crystals: apparent universality and possible application
Olivier Pagès
Université de Lorraine, France
Olivier Pagès, J Org Inorg Chem 2018, Volume: 4
DOI: 10.21767/2472-1123-C1-002