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Pardo L.C.,Group of Characterization of Materials | Pardo L.C.,Polytechnic University of Catalonia | Rovira-Esteva M.,Group of Characterization of Materials | Rovira-Esteva M.,Polytechnic University of Catalonia | And 6 more authors.
NATO Science for Peace and Security Series A: Chemistry and Biology | Year: 2010

Determination of the short- and intermediate-range structure of disordered materials is a necessary step to fully understand their properties. Despite of this, no generally accepted procedure exists to date to extract structural information from diffraction data. In this paper we describe a method which enables determination of the short-range structure of disordered molecular phases. This general method is applied to one of the first studied molecular liquids, carbon tetrachloride, and to its plastic phase being able to unravel the so called local density paradox: although molecules are closer in the liquid than in the plastic phase, the density of the former is lower than that of the later. The analysis of the short range order in both phases shows that although the minimal energy configuration allows a closer approach of molecules, it hinders the formation of the face centered cubic long range ordered lattice due to the difficulty of molecules to form stacked structures.

Martinez-Garcia J.C.,Group of Characterization of Materials | Capaccioli S.,University of Pisa | Diez S.,Group of Characterization of Materials | Tamarit J.Ll.,Group of Characterization of Materials | And 3 more authors.
Journal of Non-Crystalline Solids | Year: 2010

Orientationally disordered (OD) mixed crystals formed between cyanoadamantane (CN-A) and chloroadamantane (Cl-A) have been thermodynamically characterized by means of thermal analysis and X-ray diffraction. The dynamics of these OD mixed crystals has been studied by means of broad band dielectric spectroscopy. Results evidence that dynamics of the α-relaxation process associated with the overall molecular tumbling slows down when molecules of CN-A are substituted by molecules of Cl-A. © 2009 Elsevier B.V. All rights reserved.

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