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Updated: Jul 17, 2026

Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses
Published on: June 7, 2018
2H nuclear magnetic resonance study on the molecular motion in cyanoadamantane. II. Orientationally ordered and
S A Lusceac1, I Roggatz, J Gmeiner
1Institut für Festkörperphysik, Technische Universität Darmstadt, Hochschulstrasse 6, 64289 Darmstadt, Germany.
Abstract:
The orientationally ordered crystalline and glassy plastically crystalline phase of cyanoadamantane were investigated using (2)H NMR. Solid-echo line shape, two-dimensional spectrum, and spin-lattice relaxation were analyzed. In both phases, the molecules display solely a rotation around the molecular C(3) symmetry axis. For the orientationally ordered phase, a single correlation time characterizes the motion, and the time constant shows an Arrhenius temperature dependence. In contrast, a broad distribution G[ln(tau)] of correlation times is observed for the glassy plastically crystalline phase that leads to characteristically different NMR features such as "two-phase" spectra and pronounced nonexponential relaxation. The distribution G[ln(tau)] can be derived from a temperature independent distribution of activation energies g(E(a)), with its mean value lying significantly below the activation energy corresponding to the ordered phase. Thus, the molecular uniaxial rotation proves to be a sensitive probe for the energy landscape of the orientationally disordered glassy crystalline phase of cyanoadamantane.
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