Anomalous vibrational dynamics in the Mg2Zn11 phase

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title = "Anomalous vibrational dynamics in the Mg2Zn11 phase",
abstract = "We present a combined experimental and theoretical study of the structure and the lattice dynamics in the complex metallic alloy Mg2Zn 11, by means of neutron and x-ray scattering, as well as ab initio and empirical potential calculations. Mg2Zn11 can be seen as an intermediate step in structural complexity between the simple Laves-phase MgZn2 on one side, and the complex 1/1 approximants and quasicrystals ZnMgAl and Zn(Mg)Sc on the other. The structure can be described as a cubic packing of a triacontahedron whose center is partially occupied by a Zn atom. This partially occupied site turned out to play a major role in understanding the lattice dynamics. Data from inelastic neutron scattering evidence a Van Hove singularity in the vibrational spectrum of Mg2Zn11 for an energy as low as 4.5 meV, which is a unique feature for a nearly-close-packed metallic alloy. This corresponds to a gap opening at the Brillouin zone boundary and an interaction between a low-lying optical branch and an acoustic one, as could be deduced from the dispersion relation measured by inelastic x-ray scattering. Second, the measured phonon density of states exhibits many maxima, indicating strong mode interactions across the whole energy range. The origin of the low-energy modes in Mg2Zn11 and other features of the vibrational spectra are studied, using both ab initio and empirical potential calculations. A detailed analysis of vibrational eigenmodes is presented, linking features in the vibrational spectrum to atomic motions within structural building blocks.",
author = "H. Euchner and M. Mihalkovi{\v c} and F. G{\"a}hler and Johnson, {M. R.} and H. Schober and S. Rols and E. Suard and A. Bosak and S. Ohhashi and Tsai, {A. P.} and S. Lidin and Gomez, {C. Pay} and J. Custers and S. Paschen and {De Boissieu}, M.",
year = "2011",
month = apr,
day = "7",
doi = "10.1103/PhysRevB.83.144202",
language = "English",
volume = "83",
journal = "Physical Review B",
issn = "2469-9950",
publisher = "American Physical Society",
number = "14",