28 research outputs found
Local curvature and stability of two-dimensional systems
We propose a fast method to determine the local curvature in two-dimensional
(2D) systems with arbitrary shape. The curvature information, combined with
elastic constants obtained for a planar system, provides an accurate estimate
of the local stability in the framework of continuum elasticity theory.
Relative stabilities of graphitic structures including fullerenes, nanotubes
and schwarzites, as well as phosphorene nanotubes, calculated using this
approach, agree closely with ab initio density functional calculations. The
continuum elasticity approach can be applied to all 2D structures and is
particularly attractive in complex systems with known structure, where the
quality of parameterized force fields has not been established
Relative Stability and Local Curvature Analysis in Carbon Nanotori
We introduce a concise formalism to characterize nanometer-sized tori based
on carbon nanotubes and to determine their stability by combining {\em ab
initio} density functional calculations with a continuum elasticity theory
approach that requires only shape information. We find that the high strain
energy in nanotori containing only hexagonal rings is significantly reduced in
nanotori containing also other polygons. Our approach allows to determine local
curvature and link it to local strain energy, which is correlated with local
stability and chemical reactivity
Novel penta-graphene nanotubes: strain-induced structural and semiconductor–metal transitions
Research into novel one-dimensional (1D) materials and associated structural transitions is of significant scientific interest. It is widely accepted that a 1D system with a short-range interaction cannot have 1D phase transition at finite temperature. Herein, we propose a series of new stable carbon nanotubes by rolling up penta-graphene sheets, which exhibit fascinating well-defined 1D phase transitions triggered by axial strain. Our first-principles calculations show that such penta-graphene nanotubes (PGNTs) are dynamically stable by phonon calculations, but transform from a tri-layer structure to a highly defective single-walled nanotube at low temperature in molecular dynamics simulations. We show that moderate compressive strains can drive structural transitions of (4,4), (5,5), and (6,6) PGNTs, during which the distances of neighboring carbon dimers in the inner shell have a sudden drop, corresponding to dimer–dimer nonbonding to bonding transitions. After such transition, the tubes become much more thermally stable and undergo semiconductor–metal transitions under increasing strain. The band gaps of PGNTs are not sensitive to chirality whereas they can be tuned effectively from visible to short-wavelength infrared by appropriate strain, making them appealing materials for flexible nano-optoelectronics. These findings provide useful insight into unusual phase transitions in low-dimensional systems