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Multiple High-Temperature Transitions Driven by Dynamical Structures in NaI



M. E. Manley, J.R. Jeffries, H. Lee, Nicholas Butch, D. L. Abernathy


Multiple, consecutive high-temperature transitions in NaI involving dynamical order and/or localization in the energy-momentum spectrum but not in the average crystal structure are revealed by lattice dynamics, x-ray lattice spacing, and heat capacity measurements. Distinctive energy-momentum patterns and lattice distortions indicate dynamical structures forming within randomly stacked planes, rather than the isolated point-defect-like intrinsic localized modes predicted. Transition entropies are accounted for by vibrational entropy changes and the transition enthalpies are explained by strain energy of forming stacking-fault-like planer distortions deduced from x-ray diffraction peak shifts. The vibrational entropy of the dynamical structures stabilizes surrounding elastic distortions.
Physical Review B


phonons, intrinsically localized modes


Manley, M. , Jeffries, J. , Lee, H. , Butch, N. and Abernathy, D. (2014), Multiple High-Temperature Transitions Driven by Dynamical Structures in NaI, Physical Review B, [online], (Accessed June 12, 2024)


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Created June 26, 2014, Updated October 12, 2021