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Flexoelectric-like radial polarization of single-walled nanotubes from first-principles
- Publication Year :
- 2021
- Publisher :
- Apollo - University of Cambridge Repository, 2021.
-
Abstract
- Flexoelectricity is the polar response of an insulator to strain gradients such as bending. While the size dependence of this effect makes it weak in bulk systems in comparison to piezoelectricity, it suggests that it plays a bigger role in nanoscale systems such as thin films and nanotubes (NTs). In this paper we demonstrate using first-principles calculations that the walls of carbon nanotubes (CNTs) and transition metal dichalcogenide nanotubes (TMD NTs) are polarized in the radial direction, the strength of the polarization increasing as the size of the NT decreases. For CNTs and TMD NTs with chiral indices $(n,m)$, the radial polarization of the walls $P_R$ starts to diverge below $ C(n,m)/a = \sqrt{n^2 +nm + m^2} \sim 10$, where $C(n,m)$ is the circumference of the NT and $a$ is the lattice constant of the 2D monolayer. For CNTs, $P_R$ drops to zero above this value but for TMD NTs there is a non-zero polarization above this value, which is an ionic rather than electronic effect. The size dependence of $P_R$ in the TMD NTs is interesting: it increases gradually and reaches a maximum of $P_R \sim 100 \ \text{C/cm}^2$ at $C(n,m)/a \sim 15$, then decreases until $C(n,m)/a \sim 10$ where it starts to diverge. Measurements of the radial strain on the chalcogen atoms with respect to the 2D monolayers shows that this polarization is the result of a significantly larger strain on the outer bonds than the inner bonds, but did not offer an explanation for the peculiar size dependence. These results suggest that while the walls of smaller CNTs and TMD NTs are polarized, the walls of larger TMD NTs are also polarized due to a difference in strain on the inner and outer atoms in the walls. This result may prove useful for the application of NTs for screening in liquid or biological systems.<br />The author acknowledges support from the EPSRC Centre for Doctoral Training in Computational Methods for Materials Science under Grant No. EP/L015552/1.
- Subjects :
- Paper
Condensed Matter - Materials Science
Materials science
Condensed matter physics
Condensed Matter - Mesoscale and Nanoscale Physics
Flexoelectricity
Materials Science (cond-mat.mtrl-sci)
FOS: Physical sciences
first-principles
Condensed Matter Physics
cond-mat.mtrl-sci
Electronic, Optical and Magnetic Materials
nanotubes
Condensed Matter::Materials Science
cond-mat.mes-hall
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Electrochemistry
Materials Chemistry
flexoelectricity
Radial polarization
Electrical and Electronic Engineering
Subjects
Details
- Database :
- OpenAIRE
- Accession number :
- edsair.doi.dedup.....21be077a6590e1bf8145f10de0d326b5
- Full Text :
- https://doi.org/10.17863/cam.66052