Bond switching is responsible for nanoductility in zeolitic imidazolate framework glasses

To, Theany; Sørensen, Søren Strandskov; Yue, Yuanzheng; Smedskjær, Morten Mattrup

doi:10.1039/d1dt00096a

Cited by 19 publications

(35 citation statements)

References 39 publications

(67 reference statements)

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“…The general underestimation of the absolute values of K Ic by the model may be due to the assumption of a fully brittle fracture. Given two (or three) accessible coordination states and the presence of higher than four‐coordinated Ge species in all samples, so‐called bond switching events, which have been shown to govern fracture in various glass systems, 43,78–80 may play a role in the fracture process, inducing some nanoscale ductility. That is, when applying strain on a structure, the multiple occupied and accessible coordination states will allow for significant atomic rearrangement before fracture is obtained, hence representing a plastic fracture process.…”

Section: Resultsmentioning

confidence: 99%

Impact of network topology on the thermal and mechanical properties of lithium germanate glasses

Sørensen

Christensen

et al. 2021

J Am Ceram Soc.

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In this work, we study the structure-topology-property relations of a series of melt-quenched lithium germanate glasses. These glasses exhibit the so-called germanate anomaly, that is, the germanium atoms feature a distribution of fourcoordinated and higher coordinated germanium species, manifesting itself as anomalies in several material properties. Here, we couple variations in the number of atomic bond constraints with measured variations in thermal and mechanical properties, including thermal conductivity, Vickers hardness, and fracture toughness. For thermal conductivity, a strong correlation is found with sound velocity as well as with the volumetric constraint density. For hardness, a good correlation with volumetric constraint density is found, whereas, for fracture toughness, variations in network topology alone are insufficient to explain the composition-property relation. To account for this, we apply a recent model which incorporates knowledge of local structure, mechanical properties, and fracture patterns to predict the fracture toughness, showing a good qualitative agreement with the experimental data.

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Section: Resultsmentioning

confidence: 99%

Impact of network topology on the thermal and mechanical properties of lithium germanate glasses

Sørensen

Christensen

et al. 2021

J Am Ceram Soc.

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“…A subsequent study performed equivalent simulations for ZIF-4 and ZIF-76 (mix of imidazolate and 5-methylbenzimidazolate ligands), before investigating the structural origin of the facture behaviour. 42 Another work computed the thermal conductivity of amorphous ZIF-4, ZIF-62 and ZIF-8, which were validated by comparison with experimental values. 43 The glass was shown to have a higher conductivity than the crystal, a very unusual relation, and the atomistic models were key to investigate the structural origin of this phenomenon.…”

Section: Reactive Force Fieldsmentioning

confidence: 98%

Atomistic Models of Amorphous Metal-Organic Frameworks

Castel,

Coudert

2022

Preprint

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There is an increasing interest in the amorphous states of metal-organic frameworks (MOFs) and porous coordination polymers, which can be produced by pressure-induced amorphization, temperature-induced amorphization, melt-quenching, ball-milling, irradiation, etc. They can exhibit useful physical and chemical properties, distinct from those achievable in the crystalline states, along with greater ease of processing, and intrinsic advantages over crystals and powders, such as high transparency and mechanical robustness. However, these amorphous states are particularly challenging to characterize, and the determination of their framework structure at the microscopic scale is difficult, with only indirect structural information available from diffraction experiments. In this Perspective, we review and compare the existing methodologies available for the determination of microscopic models of amorphous MOFs, based on both experimental data and simulation methods. In particular, the atomistic models that can be obtained using Reverse Monte Carlo (RMC) methods, Continuous Random Networks (CRN), classical and ab initio molecular dynamics, reactive force fields, and simulated assembly/polymerization algorithms.

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“…Although the ZIF glasses feature nanoscale ductility via bond switching [ 226 ] and the relatively high Poisson's ratio (≈0.34) might indicate a more ductile fracture behavior, [ 82 ] the low toughness is ascribed to the preferential breakage of the weak ZnN coordination bonds (Figure 11c). Indeed, the coordination bonds control a wide range of their mechanical behavior and have also been associated with indentation‐induced shear bands, which are typically not seen in other network glasses with a fully polymerized structure.…”

Section: Emerging Glass Types With Optical Transparency and Tailored ...mentioning

confidence: 99%

“…c) Simulated bond switching mechanism in ZIF-62 glass, showing how the central Zn atom (in red) transitions from fourfold to threefold and back to fourfold coordination with N upon increasing strain (ε) from ε = 0 (left) to ε = 0.09 (middle) and ε = 0.42 (right). Adapted with permission [226]. Copyright 2021, Royal Society of Chemistry.…”

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confidence: 99%

Advancing the Mechanical Performance of Glasses: Perspectives and Challenges

et al. 2022

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in terms of deciphering structure-property relationships and the nonaffine nature of glass mechanical behavior, of computational and computer-assisted methods for accelerated materials discovery, and of physicochemical insight at glass formation and synthesis in unconventional types of materials. Despite this progress, significant questions remain as to the fundamental role of structural heterogeneity and its consequences for the predictability of mechanical properties underlying the many applications of glass. Today's challenge is to translate new understanding of the physics of disorder, glass chemistry, and surface mechanics into tools that enable future glass products with adapted elasticity, strength, and toughness. We will therefore consider fundamental advances in relation to emerging glass applications. While the aforementioned physical insights have mostly been obtained by computational simulation of model systems, and often through the examination of metallic glasses, we will here focus on glasses suitable for visible transparency, in particular silicate glasses, such as a representative of today's most prolific glass devices, ranging from ultrathin substrates to strong and visually transparent cover materials. We will further consider hybrid glasses and glass-like composite materials as emerging alternatives that may overcome the ubiquitous conflict between strength and toughness. [1] Glasses are materials that lack a crystalline microstructure and long-range atomic order. Instead, they feature heterogeneity and disorder on superstructural scales, which have profound consequences for their elastic response, material strength, fracture toughness, and the characteristics of dynamic fracture. These structure-property relations present a rich field of study in fundamental glass physics and are also becoming increasingly important in the design of modern materials with improved mechanical performance. A first step in this direction involves glass-like materials that retain optical transparency and the haptics of classical glass products, while overcoming the limitations of brittleness. Among these, novel types of oxide glasses, hybrid glasses, phase-separated glasses, and bioinspired glass-polymer composites hold significant promise. Such materials are designed from the bottom-up, building on structure-property relations, modeling of stresses and strains at relevant length scales, and machine learning predictions. Their fabrication requires a more scientifically driven approach to materials design and processing, building on the physics of structural disorder and its consequences for structural rearrangements, defect initiation, and dynamic fracture in response to mechanical load. In this article, a perspective is provided on this highly interdisciplinary field of research in terms of its most recent challenges and opportunities.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adma.202109029.

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Bond switching is responsible for nanoductility in zeolitic imidazolate framework glasses

Abstract: Understanding of the fracture mechanism of metal-organic framework glasses remains limited. Using reactive molecular dynamics simulations, we here find that three zeolitic imidazolate framework glasses exhibit pronounced nanoductility upon fracture....

Cited by 19 publications

References 39 publications

Impact of network topology on the thermal and mechanical properties of lithium germanate glasses

Impact of network topology on the thermal and mechanical properties of lithium germanate glasses

Atomistic Models of Amorphous Metal-Organic Frameworks

Advancing the Mechanical Performance of Glasses: Perspectives and Challenges

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