Chemical Bonding in Chalcogenides: The Concept of Multicenter Hyperbonding

Lee, Tae Hoon; Elliott, S. R.

doi:10.1002/adma.202000340

Cited by 78 publications

(120 citation statements)

References 62 publications

(74 reference statements)

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“…The definition of polarity index corresponds to the value of χ described in the previous study. [ 14 ]…”

Section: Multi‐center Hyperbondingmentioning

confidence: 99%

“…Here, we attempt to address the question of how to understand the interesting material properties of chalcogenide PCMs, and of some non‐PCMs, from the point of view of the multi‐center hyperbonding model developed recently through the first‐principles DFT simulations. [ 14 ] Although we focus here on the Ge 2 Sb 2 Te 5 (GST) material, the prototypical PCM, the conclusions are quite general for other PCMs and non‐PCM chalcogenides.…”

Section: Introductionmentioning

confidence: 99%

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Multi‐Center Hyperbonding in Phase‐Change Materials

Lee

Elliott

2021

Physica Rapid Research Ltrs

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A comprehensive understanding of chemical interactions underlying the network structure of chalcogenide materials is a crucial prerequisite for comprehending their microscopic structures, physicochemical properties, and capabilities for current or potential applications. However, for many chalcogenide materials, an inherent difficulty is often present in investigating their chemical properties, due to the involvement of delocalized bonding and non‐bonding (“lone‐pair”) electrons, which requires interaction mechanisms beyond that of conventional two‐center, two‐electron covalent bonding. Herein, some recent progress in the development of new interatomic interaction models for chalcogenides is reviewed, in particular focusing on the multi‐center hyperbonding model, proposed in an effort to resolve this issue. The capability of this model in elucidating a diversity of interesting material properties of phase‐change materials (PCMs) is highlighted, including Ge2Sb2Te5 (GST). These include the propensity of high coordination numbers of constituent atoms, linear triatomic bonding geometries with short and long bonds (often ascribed to the effect of a Peierls distortion), abnormally large Born effective charges of crystalline GST, large optical contrast between amorphous and crystalline GST, ultrafast crystallization speed of amorphous GST, and the chemical origin differentiating non‐PCM from PCM chalcogenide materials. Other bonding models for these materials are also briefly discussed.

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“…The definition of polarity index corresponds to the value of χ described in the previous study. [ 14 ]…”

Section: Multi‐center Hyperbondingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Multi‐Center Hyperbonding in Phase‐Change Materials

Lee

Elliott

2021

Physica Rapid Research Ltrs

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“…[62] High Born effective charge (from 4 to 6) is also considered as one of property-based fingerprints for PCM materials due to their native p-orbital bonding characteristics. [36,53] The calculation steps can be found in the Experimental Section. Second, we calculate cohesive energy (E C ).…”

Section: Analysis Of Performance Characteristics Of Screened Materialsmentioning

confidence: 99%

High‐Throughput Screening for Phase‐Change Memory Materials

Liu

Zheng

et al. 2021

Adv Funct Materials

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Phase change memory (PCM) is an emerging non-volatile data storage technology concerned by the semiconductor industry. To improve the performances, previous efforts have mainly focused on partially replacing or doping elements in the flagship Ge-Sb-Te (GST) alloy based on experimental "trialand-error" methods. Here, the current largest scale PCM materials searching is reported, starting with 124 515 candidate materials, using a rational highthroughput screening strategy consisting of criteria related to PCM characteristics. In the results, there are 158 candidates screened for PCM materials, of which ≈68% are not employed. By further analyses, including cohesive energy, bond angle analyses, and Born effective charge, there are 52 materials with properties similar to the GST system, including Ge 2 Bi 2 Te 5 , GeAs 4 Te 7 , GeAs 2 Te 4 , so on and other candidates that have not been reported, such as TlBiTe 2 , TlSbTe 2 , CdPb 3 Se 4 , etc. Compared with GST, materials with close cohesive energy include AgBiTe 2 , TlSbTe 2 , As 2 Te 3 , TlBiTe 2 , etc., indicating possible low power consumption. Through further melt-quenching molecular dynamic calculation and structural/electronic analyses, Ge 2 Bi 2 Te 5 , CdPb 3 Se 4 , MnBi 2 Te 4 , and TlBiTe 2 are found suitable for optical/electrical PCM applications, which further verifies the effectiveness of this strategy. The present study will accelerate the exploration and development of advanced PCM materials for current and future big-data applications.

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“…Several mechanisms have been previously proposed to explain the optical property of PCM materials, such as the resonant bonding, [53] metavalent bonding, [54] hyperbonding, [55] and www.advancedsciencenews.com www.pss-rapid.com three-center-four-electron bonding. [56] In contrast, some reports regard bonding as a competing ionic and covalent bonding, [57] whereas some reports believe that the optical property can be explained by the Penn gap rule.…”

Section: Doi: 101002/pssr202000441mentioning

confidence: 99%

Nucleation Dynamics of Phase‐Change Memory Materials: Atomic Motion and Property Evolution

Chen

Liu

Wang

et al. 2020

Physica Rapid Research Ltrs

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Reversible phase transitions between crystalline and amorphous phases of phase‐change memory (PCM) materials are the physical basis of PCM. Applications of PCM in multilevel memory, in‐memory computing, and neuromorphic computing require a precise control of material's structure/property to achieve signals beyond binary (0/1), where recrystallization is the key process because it is smooth compared with violent amorphization. By molecular dynamic simulations and electronic structure analyses based on density functional theory, nucleation dynamics during recrystallization are investigated from the point of view of atomic motions and property evolutions. Atomic motions are examined individually rather than statistically. According to the results, an atomic picture of the growth of the nucleus is described in detail, where the competition between the potential seeds of nucleus plays a critical role. The electron polarization during recrystallization is mapped to the linearly aligned atom chains. Further analyses of the Born effective charge confirm the delocalization of the electrons in the atom chains. Also, a large p‐orbital‐axial Born effective charge is observed in long‐range atom chains, which suggests a kind of resonance enhancement of electronic delocalization. These dynamics of nucleation in recrystallization provide references for the fine control of PCM performances.

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Chemical Bonding in Chalcogenides: The Concept of Multicenter Hyperbonding

Cited by 78 publications

References 62 publications

Multi‐Center Hyperbonding in Phase‐Change Materials

Multi‐Center Hyperbonding in Phase‐Change Materials

High‐Throughput Screening for Phase‐Change Memory Materials

Nucleation Dynamics of Phase‐Change Memory Materials: Atomic Motion and Property Evolution

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