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Q-Dependent Collective Relaxation Dynamics of Glass-Forming Liquid Ca0.4K0.6(NO3)1.4 Investigated by Wide-Angle Neutron Spin-Echo



Peng Luo, Yanqin Zhai, Peter Falus, Victoria Garcia Sakai, Monika Hartl, Maiko Kofu, Kenji Nakajima, Antonio Faraone, Y. Z


Employing high-intensity wide-angle neutron spin-echo spectroscopy, we measured the coherent intermediate scattering function of the prototypical ionic glass former Ca0.4K0.6(NO3)1.4 in the equilibrium and supercooled liquid state from 383 to 519 K, covering the full range of the structure factor peak and valley from 0.80 Å−1 to 2.82 Å−1. With unprecedent accuracy, the data reveal a clear two-step relaxation: the exponential, fast β-process and the stretched exponential, slow α-process. The Q-dependence of relaxation time, amplitude, and stretching exponent of α-relaxation exhibits marked de Gennes narrowing. For all studied Q's the relative amplitude of αrelaxation decreases with temperature until 470 K followed by a plateau in the equilibrium liquid state. The temperature dependence of the stretching exponent and the relaxation time indicate that modifications of the relaxation mechanisms at the local length scales, manifested as temperature independent dynamic heterogeneity and smaller deviations from Arrhenius behavior, have occurred even above the temperature where the α-relaxation transits to the Johari-Goldstein β-relaxation.
Nature Communications


Luo, P. , Zhai, Y. , Falus, P. , Garcia Sakai, V. , Hartl, M. , Kofu, M. , Nakajima, K. , Faraone, A. and Z, Y. (2022), Q-Dependent Collective Relaxation Dynamics of Glass-Forming Liquid Ca<sub>0.4</sub>K<sub>0.6</sub>(NO<sub>3</sub>)<sub>1.4</sub> Investigated by Wide-Angle Neutron Spin-Echo, Nature Communications (Accessed April 12, 2024)
Created April 18, 2022, Updated November 29, 2022