Metavalent Bonding in Crystalline Solids: How Does It Collapse?

Guarneri, L; Jakobs, Stefan; Hoegen, A. von; Maier, S.; Xu, Ming; Zhu, Minhao; Wahl, Sophia; Teichrib, Christian; Zhou, Yiming; Cojocaru‐Mirédin, Oana; Raghuwanshi, Mohit; Schön, Carl‐Friedrich; Drögeler, Marc; Stampfer, Christoph; Lobo, R. P. S. M.; Piarristeguy, Andréa; Pradel, Annie; Raty, Jean‐Yves; Wuttig, Matthias

doi:10.1002/adma.202102356

Cited by 91 publications

(99 citation statements)

References 61 publications

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“…We now know that metavalent bonding has at least two well-defined borders to the covalent and iono-covalent regime of the map. This work demonstrates that metavalent bonding can be weakened not only by increased electron-sharing (as shown previously [8,9]), but also through an increase in electron transfer, where the former can result in structural distortions (e.g. Peierls distortion).…”

supporting

confidence: 78%

“…In particular, the border between metavalent and covalent bonding has been studied recently. [8,9] It was shown that several bonding descriptors, including Z* and ε∞ as well as the bond breaking (i.e. the PME) showed a discontinuous change upon the transition from metavalent to covalent bonding.…”

Section: Introductionmentioning

confidence: 99%

“…4) and it has already been used successfully to study the boundary between metavalent and covalent bonding. [8,9] In this work we focus on the boundary between metavalent and iono-covalent bonding. From Fig.…”

mentioning

confidence: 99%

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Discovering Electron‐Transfer‐Driven Changes in Chemical Bonding in Lead Chalcogenides (PbX, where X = Te, Se, S, O)

et al. 2020

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Understanding chemical bonding is of significant interest since it allows us to comprehend and tailor certain material properties, [1,2] which could be utilized, e.g., to optimize phase-change materials (PCMs) [3-7] or thermoelectrics. [8,9] The first steps to understand the nature of the chemical bond were already taken almost a century ago by Linus Pauling [10] and others. [11,12] In the meantime, enormous developments have taken place in both, quantum-mechanical and experimental techniques, [13-15] which help us to explore chemical bonding with unprecedented detail. Recently, these advances have also led to the concept of metavalent bonding (MVB), describing a bonding mechanism in between electron delocalization (i.e., metallic bonding) and electron localization at the ion cores (i.e., ionic bonding) as well as within the interatomic region (i.e., covalent bonding). [16-18] Metavalent bonding has been categorized by combining both quantummechanical and experimentally accessible bonding descriptors. [16-18] The Understanding the nature of chemical bonding in solids is crucial to comprehend the physical and chemical properties of a given compound. To explore changes in chemical bonding in lead chalcogenides (PbX, where X = Te, Se, S, O), a combination of property-, bond-breaking-, and quantummechanical bonding descriptors are applied. The outcome of the explorations reveals an electron-transfer-driven transition from metavalent bonding in PbX (X = Te, Se, S) to iono-covalent bonding in β-PbO. Metavalent bonding is characterized by adjacent atoms being held together by sharing about a single electron (ES ≈ 1) and small electron transfer (ET). The transition from metavalent to iono-covalent bonding manifests itself in clear changes in these quantum-mechanical descriptors (ES and ET), as well as in property-based descriptors (i.e., Born effective charge (Z*), dielectric function ε(ω), effective coordination number (ECoN), and mode-specific Grüneisen parameter (γ TO)), and in bond-breaking descriptors. Metavalent bonding collapses if significant charge localization occurs at the ion cores (ET) and/or in the interatomic region (ES). Predominantly changing the degree of electron transfer opens possibilities to tailor material properties such as the chemical bond (Z*) and electronic (ε ∞) polarizability, optical bandgap, and optical interband transitions characterized by ε 2 (ω). Hence, the insights gained from this study highlight the technological relevance of the concept of metavalent bonding and its potential for materials design.

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confidence: 78%

Section: Introductionmentioning

confidence: 99%

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Discovering Electron‐Transfer‐Driven Changes in Chemical Bonding in Lead Chalcogenides (PbX, where X = Te, Se, S, O)

et al. 2020

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“…The concentration of O atoms shows a strong correlation with Ge atoms, as expected from the phase separation tendency predicted in our DFMD model of the Ge‐Sb‐O glass. It has been established that crystalline PCMs are stabilized by metavalent bonding (MVB), [ 56 , 57 , 58 ] while covalent bonding prevails in amorphous PCMs. The bonding difference between the two phases is evidenced by their distinct dielectric functions, [ 59 ] and be revealed in direct measurements of bond rupture events using APT.…”

Section: Resultsmentioning

confidence: 99%

Designing Conductive‐Bridge Phase‐Change Memory to Enable Ultralow Programming Power

Yang

Wang

et al. 2022

Advanced Science

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Phase‐change material (PCM) devices are one of the most mature nonvolatile memories. However, their high power consumption remains a bottleneck problem limiting the data storage density. One may drastically reduce the programming power by patterning the PCM volume down to nanometer scale, but that route incurs a stiff penalty from the tremendous cost associated with the complex nanofabrication protocols required. Instead, here a materials solution to resolve this dilemma is offered. The authors work with memory cells of conventional dimensions, but design/exploit a PCM alloy that decomposes into a heterogeneous network of nanoscale crystalline domains intermixed with amorphous ones. The idea is to confine the subsequent phase‐change switching in the interface region of the crystalline nanodomain with its amorphous surrounding, forming/breaking “nano‐bridges” that link up the crystalline domains into a conductive path. This conductive‐bridge switching mechanism thus only involves nanometer‐scale volume in programming, despite of the large areas in contact with the electrodes. The pore‐like devices based on spontaneously phase‐separated Ge13Sb71O16 alloy enable a record‐low programming energy, down to a few tens of femtojoule. The new PCM/fabrication is fully compatible with the current 3D integration technology, adding no expenses or difficulty in processing.

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“…[ 21–25 ] Strategies such as band‐engineering, carrier scattering modulation, nanostructuring, resonant doping, and energy filtering have been well reported to enhance various aspects of thermoelectrics. [ 17,26–31 ]…”

Section: Introductionmentioning

confidence: 99%

Upcycling Silicon Photovoltaic Waste into Thermoelectrics

et al. 2022

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Two decades after the rapid expansion of photovoltaics, the number of solar panels reaching end‐of‐life is increasing. While precious metals such as silver and copper are usually recycled, silicon, which makes up the bulk of a solar cells, goes to landfills. This is due to the defect‐ and impurity‐sensitive nature in most silicon‐based technologies, rendering it uneconomical to purify waste silicon. Thermoelectrics represents a rare class of material in which defects and impurities can be engineered to enhance the performance. This is because of the majority‐carrier nature, making it defect‐ and impurity‐tolerant. Here, the upcycling of silicon from photovoltaic (PV) waste into thermoelectrics is enabled. This is done by doping 1% Ge and 4% P, which results in a figure of merit (zT) of 0.45 at 873 K, the highest among silicon‐based thermoelectrics. The work represents an important piece of the puzzle in realizing a circular economy for photovoltaics and electronic waste.

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Metavalent Bonding in Crystalline Solids: How Does It Collapse?

Cited by 91 publications

References 61 publications

Discovering Electron‐Transfer‐Driven Changes in Chemical Bonding in Lead Chalcogenides (PbX, where X = Te, Se, S, O)

Discovering Electron‐Transfer‐Driven Changes in Chemical Bonding in Lead Chalcogenides (PbX, where X = Te, Se, S, O)

Designing Conductive‐Bridge Phase‐Change Memory to Enable Ultralow Programming Power

Upcycling Silicon Photovoltaic Waste into Thermoelectrics

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