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Martinez-Garcia JC, Tamarit JL, Capaccioli S, et al. Alpha-relaxation dynamics of orientanionally disordered mixed crystals composed of Cl-adamantane and CN-adamantane. J Chem Phys. 2010;132(16):164516doi: 10.1063/1.3397997.
Martinez-Garcia, J. C., Tamarit, J. L., Capaccioli, S., Barrio, M., Veglio, N., & Pardo, L. C. (2010). Alpha-relaxation dynamics of orientanionally disordered mixed crystals composed of Cl-adamantane and CN-adamantane. The Journal of chemical physics, 132(16), 164516. https://doi.org/10.1063/1.3397997
Martinez-Garcia, J C, et al. "Alpha-relaxation dynamics of orientanionally disordered mixed crystals composed of Cl-adamantane and CN-adamantane." The Journal of chemical physics vol. 132,16 (2010): 164516. doi: https://doi.org/10.1063/1.3397997
Martinez-Garcia JC, Tamarit JL, Capaccioli S, Barrio M, Veglio N, Pardo LC. Alpha-relaxation dynamics of orientanionally disordered mixed crystals composed of Cl-adamantane and CN-adamantane. J Chem Phys. 2010 Apr 28;132(16):164516. doi: 10.1063/1.3397997. PMID: 20441297.
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J Chem Phys. 2010 Apr 28;132(16):164516. doi: 10.1063/1.3397997.

Alpha-relaxation dynamics of orientanionally disordered mixed crystals composed of Cl-adamantane and CN-adamantane.

The Journal of chemical physics

J C Martinez-Garcia, J Ll Tamarit, S Capaccioli, M Barrio, N Veglio, L C Pardo

Affiliations

  1. Departament de Física i Enginyeria Nuclear, Grup de Caracterització de Materials, ETSEIB, Diagonal 647, Universitat Politècnicade Catalunya, 08028 Barcelona, Spain.

PMID: 20441297 DOI: 10.1063/1.3397997

Abstract

The alpha-relaxation dynamics of 1-cyano-adamantane (CNA) and its mixtures with 1-chloro-adamantane (ClA) has been studied by means of broadband dielectric spectroscopy. The existence of orientationally disordered (OD) face centered cubic mixed crystals (ClA(1-X)CNA(X)) for 0.5 < or = X < or = 1 has been put in evidence by thermodynamics and structural analyses. In addition to the OD phase of CNA, mixed crystals with compositions higher than the equimolar one exhibit a freezing of the orientational degrees of freedom into a glassy state, which involves also a strong increase of the antiferroelectric order at temperatures higher than the dielectric glass transition temperature. This experimental evidence is revealed by a stairlike effect in the variation of the Kirkwood factor with the temperature as a consequence of a twin effect in the dielectric strength without any anomaly in the temperature-density curves. The characteristic relaxation times are analyzed as a function of temperature and mole fraction. By setting a common temporal origin ("isochronal origin") at tau(T(g)) = 100 s for each mole fraction, it emerges that the substitution of ClA molecules by those of CNA (diminution of X) gives rise to a slow down in the dynamics, despite that the molecular volume of ClA molecules are smaller than those of CNA. This fact goes along and is accompanied by a diminution of the lattice packing with the decrease of composition. It is also shown that the heterogeneities produced by the concentration fluctuations due to the chemical disorder are the main contribution to the non-exponential character of the alpha-relaxation peaks.

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