Coexistence of Normal and Auxetic Behavior in a Thermally and Chemically Stable sp³ Nanothread: Poly[5]asterane

Abstract

A one-dimensional nanostructure with sp -hybridized carbon atoms, namely, poly[5]asterane (PA), is predicted by means of electronic structure calculations and reactive molecular dynamics simulations. Thermochemical analysis based on homodesmotic reactions showed that the formation of poly[5]asterane is more favorable than that of polytriangulane and comparable to that of polytwistane. A plane-wave DFT approach gave a computed Young's modulus of about 0.84 TPa, which is quite promising and comparable to those of other sp -hybridized nanothreads. Simulations of the desorption of hydrogen atoms from PA showed a high activation energy (E ≈52 kcal mol ), which again indicates substantial chemical stability. Interestingly, PA was shown to exhibit auxetic behavior (negative Poisson's ratio). Thus, PA is advocated as a new mechanically and chemically stable nanothread with exotic auxetic behavior.

Reactive Molecular Dynamics Simulations of Self-Assembly of Polytwistane and Its Application for Nanofibers

“…ReaxFF potential, where a general relationship between bond length and bond order and between bond order and bond energy is explicitly considered, predicts reasonable dissociation of bonds. − Other valence terms (angle and torsion) are defined in terms of the same bond orders to ensure that they converge to zero as the bonds break. ReaxFF has been applied intensively to study hydrocarbon systems and on carbon-based nanostructures. ,,− Additionally, because ReaxFF includes van der Waals (vdW) interaction appropriately, it is suitable to study material aggregation. Hence, the ReaxFF potential performs reasonably well when the model system is under strain or even at around fracture region because beyond “harmonic conditions” can be captured.…”

“…The estimated Young moduli of sp 3 -hybridized (3,0) and (2,2) carbon nanotubes (CNTs) are significantly higher than that of familiar sp 2 -hybridized CNTs. As a result, there has been a significant interest to computationally study the mechanical properties of one-dimensional (1D) nanostructures consisting of sp 3 -hybridized carbons, such as nanothreads, , PT, polytriangulane, and poly[5]­asterane as they can also be potential candidates to compete with sp 2 -hybridized CNTs and graphene when hardness and mechanical stability of the materials are of interest. ,, The mechanical properties of DNTs have been computed using density functional theory (DFT) and classical force fields such as adaptive intermolecular reactive empirical bond order (AIREBO) and reactive force field (ReaxFF), which show that classical force fields worked reasonably well for such systems . Very recently, Chen et al applied a computational technique and proposed possible formation of saturated singly substituted 1D nanothreads of the (CH) 5 E and (CH) 5 CR type, where E is a heteroatom and R is a substituent by adopting a symmetry condition .…”

Unique Omnidirectional Negative Poisson’s Ratio in δ-Phase Carbon Monochalcogenides

“…Most solids (metals, polymers, ceramics, etc.) realize ν ∈ [0.25, 0.35], while auxetic materials have a negative Poisson’s ratio (NPR, ν < 0). , The first artificial auxetic material with re-entrant structure was presented by Lakes in 1982 and subsequently attracted a lot of attention because of excellent energy absorption as a result of the NPR. − Auxetic materials from the microscale to the nanoscale find applications in bioprostheses, thermal superinsulators, composites, piezoelectric energy harvesters, vibration dampers, and sensors, for example.…”

Inserting auxeticity into graphene oxide via bottom-up strategy

“…Auxetic materials always possess a high shear modulus, which quantifies the capacity of a material to withstand shear strain during plastic deformation 37 . The capacity of a material to endure shear strain increases with its shear modulus, and as a result, the likelihood that it would fail during usage decreases.…”