Elasticity, Flexibility, and Ideal Strength of Borophenes

The mechanical properties of 2D boron—borophene—are studied by first‐principles calculations. The recently synthesized borophene with a 1/6 concentration of hollow hexagons (HH) is shown to have in‐plane modulus C up to 210 N m−1 and bending stiffness as low as D = 0.39 eV. Thus, its Foppl–von Karma...

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Bibliographic Details
Published in:Advanced functional materials 2017-03, Vol.27 (9), p.np-n/a
Main Authors: Zhang, Zhuhua, Yang, Yang, Penev, Evgeni S., Yakobson, Boris I.
Format: Article
Language:English
Subjects:
2D boron
Boron
Borophene
Breaking
Chemical bonds
DFT calculations
Ductile fracture
Elasticity
Flexibility
Graphene
Hexagons
Materials science
Mechanical properties
Phase transformations
Phase transitions
Sheets
Stiffness
strength
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Summary:The mechanical properties of 2D boron—borophene—are studied by first‐principles calculations. The recently synthesized borophene with a 1/6 concentration of hollow hexagons (HH) is shown to have in‐plane modulus C up to 210 N m−1 and bending stiffness as low as D = 0.39 eV. Thus, its Foppl–von Karman number per unit area, defined as C/D, reaches 568 nm−2, over twofold higher than graphene's value, establishing the borophene as one of the most flexible materials. Yet, the borophene has a specific modulus of 346 m2 s−2 and ideal strength of 16 N m−1, rivaling those (453 m2 s−2 and 34 N m−1) of graphene. In particular, its structural fluxionality enabled by delocalized multicenter chemical bonding favors structural phase transitions under tension, which result in exceptionally small breaking strains yet highly ductile breaking behavior. These mechanical properties can be further tailored by varying the HH concentration, and the boron sheet without HHs can even be stiffer than graphene against tension. The record high flexibility combined with excellent elasticity in boron sheets can be utilized for designing advanced composites and flexible devices. Borophene is a graphene analog for boron. Here, it is predicted that borophene, albeit being lighter than graphene, combines unprecedented flexibility with excellent in‐plane elasticity, rendering it as an atomic membrane that is easiest to bend yet hard to stretch. Moreover, borophene can exceptionally resist considerably high loading even when extremely stretched, due to unique tension‐induced structural phase transitions.
ISSN:1616-301X
1616-3028
DOI:10.1002/adfm.201605059