Signature of a polyamorphic transition in the THz spectrum of vitreous GeO2

23 Dec 2015  ·  Cunsolo Alessandro, Li Yan, Kodituwakku Chaminda N., Wang Shibing, Antonangeli Daniele, Bencivenga Filippo, Battistoni Andrea, Verbeni Roberto, Tsutsui Satoshi, Baron Alfred Q. R., Mao Ho-Kwang, Bolmatov Dima, Cai Yong Q. ·

The THz spectrum of density fluctuations, $S(Q, \omega)$, of vitreous GeO$_2$ at ambient temperature was measured by inelastic x-ray scattering from ambient pressure up to pressures well beyond that of the known $\alpha$-quartz to rutile polyamorphic (PA) transition. We observe significant differences in the spectral shape measured below and above the PA transition, in particular, in the 30-80 meV range... Guided by first-principle lattice dynamics calculations, we interpret the changes in the phonon dispersion as the evolution from a quartz-like to a rutile-like coordination. Notably, such a crossover is accompanied by a cusp-like behavior in the pressure dependence of the elastic response of the system. Overall, the presented results highlight the complex fingerprint of PA phenomena on the high-frequency phonon dispersion. read more

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Disordered Systems and Neural Networks Materials Science Statistical Mechanics Chemical Physics