In traditional materials science, structural disorder tends to break the symmetry of the lattice. In this work, however, we studied a case which may be opposite to this intuition. The prototypical phase change material, GeTe, undergoes the phase transition from the rhombohedral structure to a more symmetric cubic one at ∼625 K. Using ab initio molecular dynamics simulations, we demonstrated that even in the cubic phase, the lattice is constructed by random short and long bonds, instead of bonds with a uniform length. Such bifurcation of the bond lengths enabled by Peierls-like distortion persists in the entire temperature range (0-900 K), yet with different degrees of disorder, e.g., the atoms are distorted along a certain direction in the rhombohedral phase (i.e., structural order) but the distortion varies stochastically in terms of direction and amplitude at high T (i.e., structural disorder). A more symmetric lattice frame coexisting with severe local structural disorder is the signature of this cubic GeTe. Our simulations have provided a theoretical support on the disordered Peierls-like distortion in the high-T cubic phase discovered earlier by X-ray experiments. By modulating the physical properties that different degrees of disorder may induce, we are able to design better functional materials for various applications in electronic and photonic devices.

Structural disorder in the high-temperature cubic phase of GeTe / Xu, M.; Lei, Z.; Yuan, J.; Xue, K.; Guo, Y.; Wang, S.; Miao, X.; Mazzarello, R.. - In: RSC ADVANCES. - ISSN 2046-2069. - 8:31(2018), pp. 17435-17442. [10.1039/c8ra02561d]

Structural disorder in the high-temperature cubic phase of GeTe

Mazzarello R.
2018

Abstract

In traditional materials science, structural disorder tends to break the symmetry of the lattice. In this work, however, we studied a case which may be opposite to this intuition. The prototypical phase change material, GeTe, undergoes the phase transition from the rhombohedral structure to a more symmetric cubic one at ∼625 K. Using ab initio molecular dynamics simulations, we demonstrated that even in the cubic phase, the lattice is constructed by random short and long bonds, instead of bonds with a uniform length. Such bifurcation of the bond lengths enabled by Peierls-like distortion persists in the entire temperature range (0-900 K), yet with different degrees of disorder, e.g., the atoms are distorted along a certain direction in the rhombohedral phase (i.e., structural order) but the distortion varies stochastically in terms of direction and amplitude at high T (i.e., structural disorder). A more symmetric lattice frame coexisting with severe local structural disorder is the signature of this cubic GeTe. Our simulations have provided a theoretical support on the disordered Peierls-like distortion in the high-T cubic phase discovered earlier by X-ray experiments. By modulating the physical properties that different degrees of disorder may induce, we are able to design better functional materials for various applications in electronic and photonic devices.
2018
GeTe; Peierls distortion; ferroelectricity
01 Pubblicazione su rivista::01a Articolo in rivista
Structural disorder in the high-temperature cubic phase of GeTe / Xu, M.; Lei, Z.; Yuan, J.; Xue, K.; Guo, Y.; Wang, S.; Miao, X.; Mazzarello, R.. - In: RSC ADVANCES. - ISSN 2046-2069. - 8:31(2018), pp. 17435-17442. [10.1039/c8ra02561d]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11573/1465795
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