Static dielectric response and Born effective charge of BN nanotubes from {\it ab initio} finite electric field calculations

TL;DR

This study uses ab initio finite electric field calculations to analyze the static dielectric response and Born effective charges of BN nanotubes, revealing chirality-dependent oscillations and diameter-related behaviors.

Contribution

First ab initio investigation of BN nanotubes' dielectric response and Born effective charge using finite electric field method, highlighting chirality and diameter effects.

Findings

Ionic contribution significantly affects dielectric response.

Pronounced chirality-dependent oscillations in polarizability.

Transverse response resembles a conducting cylindrical shell.

Abstract

{\it Ab initio} investigations of the full static dielectric response and Born effective charge of BN nanotubes (BN-NTs) have been performed for the first time using finite electric field method. It is found that the ionic contribution to the static dielectric response of BN-NTs is substantial and also that a pronounced chirality-dependent oscillation is superimposed on the otherwise linear relation between the longitudinal electric polarizability and the tube diameter ($D$), as for a thin dielectric cylinderical shell. In contrast, the transverse dielectric response of the BN-NTs resemble the behavior of a thin (non-ideal) conducting cylindrical shell of a diameter of $D+4$\AA$ $, with a screening factor of 2 for the inner electric field. The medium principal component $Z_y^*$ of the Born effective charge corresponding to the transverse atomic displacement tangential to the BN-NT surface, has a pronounced $D$-dependence (but independent of chirality), while the large longitudinal component $Z_z^*$ exhibits a clear chirality dependence (but nearly $D$-independent), suggesting a powerful way to characterize the diameter and chirality of a BN-NT.