Local order in amorphous<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mi mathvariant="normal">Ge</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">Sb</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">Te</mml:mi><mml:mn>5</mml:mn></mml:msub></mml:mrow></mml:math>and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi mathvariant="normal">Ge</mml:mi><mml:msub><mml:mi

Jóvári, P.; Kaban, I.; Steiner, Jorge Rios; Beuneu, B.; Schöps, A.; Webb, Mark

doi:10.1103/physrevb.77.035202

Cited by 153 publications

(112 citation statements)

References 19 publications

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“…Their structures are in sharp contradiction to information found in experiment [2][3][4] and in more extensive simulations of GST [5,6]. In [6] we suggested that (much smaller) vacancies are essential for the rapid phase transition in GST and in Ge=Te alloys [7].…”

contrasting

confidence: 52%

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Comment on “Formation of Large Voids in the Amorphous Phase-Change MemoryGe2Sb2Te5Alloy”

Akola

Jones

2010

Phys. Rev. Lett.

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contrasting

confidence: 52%

“…The calculated total coordination numbers in [1] (Ge, 5.25; Sb, 5.67; Te, 3.98) are vastly higher than those found in previous calculations [5,6] and in any experimental work on this material (x-ray diffraction, neutron diffraction, EXAFS) [2][3][4]. The authors neither compare with any of this work nor provide error estimates on their values.…”

contrasting

confidence: 42%

Comment on “Formation of Large Voids in the Amorphous Phase-Change MemoryGe2Sb2Te5Alloy”

Akola

Jones

2010

Phys. Rev. Lett.

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“…59 Furthermore, this configuration is unstable; i.e., the system will relax without an energy barrier to a lower energy configuration ͑see below͒. Therefore, this key finding can be used to identify the possibility of generating disordered structures by a standard geometric optimization of high energy configurations with occupation of the tetrahedral sites by Ge atoms.…”

Section: B Intermediate Phase Between Crystalline and Amorphousmentioning

confidence: 99%

“…59 An analysis of the RS m-GST structure shows that tetrahedral Ge atoms surrounded by Te atoms can be obtained by shifting Ge along the RS ͓111͔ or ͓111͔ directions ͑hexagonal c axis͒, Fig. 1͑a͒.…”

Section: B Intermediate Phase Between Crystalline and Amorphousmentioning

confidence: 99%

“…51,52 The latter interpretation is supported by recently first-principles calculations reported by Da Silva et al, 32 which is also consistent with previous studies for bulk GeTe in the distorted RS structure. 51,52 Based on experimental and theoretical studies, it has been suggested that a-GST is characterized by the presence of fourfold coordinated Ge atoms, 37,42,46,48,50,[53][54][55][56][57][58][59][60] in which the sum of the occurrences of GeTe 4 , Ge͑SbTe 3 ͒, and Ge͑GeTe 3 ͒ is about 66%, 59 which is similar to the local environments observed in amorphous GeTe for GeTe 4 and Ge͑GeTe 3 ͒. 61 Ge-Ge and Ge-Sb bonds are found in those motifs, which is assumed to be due to disorder effects, since they are not present in the crystalline phases.…”

Section: Introductionmentioning

confidence: 99%

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Atomistic origins of the phase transition mechanism in Ge2Sb2Te5

Silva

Walsh

Wei

et al. 2009

Journal of Applied Physics

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Tricritical behavior of the RI-RV rotator phase transition in a mixture of alkanes with nanoparticles J. Chem. Phys. 135, 134505 (2011) Pressure-induced amorphization in mayenite (12CaO·7Al2O3) J. Chem. Phys. 135, 094506 (2011) Influence of Al2O3 crystallization on band offsets at interfaces with Si and TiNx Appl. Phys. Lett. 99, 072103 (2011) Temperature induced transition from hexagonal to circular pits in graphite oxidation by O2 Appl. Phys. Lett. 99, 044102 (2011) Phase transformation of Ho2O3 at high pressure J. Appl. Phys. 110, 013526 (2011) Additional information on J. Appl. Phys. The fast and reversible phase transition mechanism between crystalline and amorphous phases of Ge 2 Sb 2 Te 5 has been in debate for several years. Through employing first-principles density functional theory calculations, we identify a direct structural link between the metastable crystalline and amorphous phases. The phase transition is driven by the displacement of Ge atoms along the rocksalt ͓111͔ direction from stable octahedron to high energy unstable tetrahedron sites close to the intrinsic vacancy regions, which generates a high energy intermediate phase between metastable and amorphous phases. Due to the instability of Ge at the tetrahedron sites, the Ge atoms naturally shift away from those sites, giving rise to the formation of local-ordered fourfold motifs and the long-range structural disorder. Intrinsic vacancies, which originate from Sb 2 Te 3 , lower the energy barrier for Ge displacements, and hence, their distribution plays an important role in the phase transition. The high energy intermediate configuration can be obtained experimentally by applying an intense laser beam, which overcomes the thermodynamic barrier from the octahedron to tetrahedron sites. The high figure of merit of Ge 2 Sb 2 Te 5 is achieved from the optimal combination of intrinsic vacancies provided by Sb 2 Te 3 and the instability of the tetrahedron sites provided by GeTe.

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Reverse M onte C arlo Simulations of Noncrystalline Solids

Kohara

Pusztai

2022

Atomistic Simulations of Glasses

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Local order in amorphousGe2Sb2Te5andGe

Cited by 153 publications

References 19 publications

Comment on “Formation of Large Voids in the Amorphous Phase-Change MemoryGe2Sb2Te5Alloy”

Comment on “Formation of Large Voids in the Amorphous Phase-Change MemoryGe2Sb2Te5Alloy”

Atomistic origins of the phase transition mechanism in Ge2Sb2Te5

Reverse M onte C arlo Simulations of Noncrystalline Solids

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