Metamorphosis in carbon network: From penta-graphene to biphenylene under uniaxial tension

Abstract

The power of polymorphism in carbon is vividly manifested by the numerous applications of carbon-based nano-materials. Ranging from environmental issues to biomedical applications, it has the potential to address many of today's dire problems. However, an understanding of the mechanism of transformation between carbon allotropes at a microscopic level is crucial for its development into highly desirable materials. In this work we report such a phase transformation between two carbon allotropes, from penta-graphene (a semiconductor) into biphenylene (a metal) under uniaxial loading. Using density functional theory we demonstrated that the phase transformation occurs through a synchronized reorganization of the carbon atoms with a simultaneous drop in energy. The results of this work confirms that penta-graphene is a metastable structure. On the other hand, a rigorous analysis of biphenylene suggests that it is an energetically, mechanically, dynamically and thermally stable structure, both in the form of a sheet and a tube. Its electronic structure suggests that it is metallic in both these forms.Therefore, this work unravels the possibility of phase transition in 2-D carbon systems and thereby designing nano-materials capable of altering their properties in an instant. Furthermore, heating biphenylene sheet at a high temperature (5000K) revealed another phase transformation into a more stable hexa-graphene like structure. This proposes thermal annealing as a possible method of synthesizing one 2-D carbon allotrope from another.

Hydrogenated Ψ-graphene as an ultraviolet optomechanical sensor

“…Based on the total energy calculations of a structure, all allotropes of graphene have less stability than graphene itself. As it is reported, graphenes' total energy is À9.23 to À9.28 eV per atom, [29][30][31] while this value for biphenylene is À8.82 eV per atom 30,32 and for graphyne is À8.3 to À8.51 eV per atom. 31,32 Nevertheless, allotropes of graphene have more strain sustainability than graphene itself; e.g.…”

Structural stability of single-layer PdSe2 with pentagonal puckered morphology and its nanotubes

“…In contrast to graphene, which is, in fact, a one-atom-thick material, penta-graphene has nonzero thickness (1.2 Å). It was early theoretically proposed to be a thermodynamically and mechanically stable allotrope of graphene, however, further theoretical investigations have shown that it is mechanically, 31 thermodynamically, 32 symmetrically and topologically, 16 as well as energetically and kinetically unstable. 33 In particular, it has been shown that mutually perpendicular top and bottom sublattices create uncompensated mechanical stress, which consequently causes strong topological instability and bending of the 2D crystalline lattice.…”

Emerging Applications of Elemental 2D Materials

“…While theoretical studies predict that these phases are potential stable (although relatively less so than graphene), external stimuli or intrinsic defects may substantially reduce their stability. For example, Rahaman et al suggested that applying uniaxial loading transforms penta-graphene to a more energetically stable metallic isomer, biphynylene, [43] while Shahrokhi et al predicted that penta-graphene becomes much less stable under strain. [44] Among group III elements, especially for 2D aluminum (aluminene) and 2D boron (borophene), a number of allotropes have been theoretically predicted with somewhat complex multiatomic unit cells.…”

“…Qin et al demonstrated vapor phase deposition of selenene flakes, t = 5–15 nm and lateral dimensions ≈10 µm, in a tube furnace at ≈200 °C under flowing Ar . These flakes exhibited lateral growth along…”