Dynamic analysis of boron nitride nanotube using different boundary conditions under influence of vacancy defect: Insights from finite element method

Abstract

In this paper, the effect of defects such as atomic vacancies (single atom vacancies like boron atom(Vb) or nitrogen atom vacancy(Vn) and di-atomic vacancies(VB-N) corresponds to vacancy of one boron and adjacent one nitrogen atom) on the vibrational behaviour of a single-walled boron nitride nanotube (SWBNNT) are investigated using finite element modelling in context of their applicability as mass sensors. The change in resonance frequency produced by vacancy defects at various points throughout the span when a mass is connected to the tip has also been examined. Space frames with three-dimensional components and point masses have been used to explain the cantilevered armchair (5, 5) and zigzag (10, 0) SW-BNNT with changing vacancy defects. The position of atomic vacancy has been varied (i.e., at 25 %, 50 % and 90 % of length from fixed end) to investigate the effect of location of defect along the length on the resonance behaviour of SW-BNNT. Further defective BNNTs have been analysed in such a way that the same can be used as nanomechanical resonator for detecting small mass of the order of femtogram level. For this,a small mass (varying from 10-20 to 10−25kg) is attached at the tip of cantilevered SW-BNNT. Substantial drop in frequency shift is observed when the position of defect moves toward the free end. the excitation frequency of defective BNNT is larger near the free end as compared to pristine one.