Single-Walled boron nitride nanotubes interaction with nickel, titanium, palladium, and gold metal atoms- A first-principles study K.W. Kayang a , E. Nyankson a , J.K. Efavi a , E.K.K. Abavare c , G. Garu b , B. Onwona-Agyeman a , A. Yaya a, * a Department of Materials Science and Engineering, CBAS, University of Ghana, Ghana b Department of Physics, CBAS, University of Ghana, Ghana c Department of Physics KNUST, Kumasi, Ghana ARTICLE INFO Keywords: Boron nitride nanotubes Density functional theory Transition metals Fermi energy Band gap ABSTRACT Ab initio calculations based on density functional theory was carried out to study the electronic properties of (3,3), (4,2), (5,2) and (6,0) boron nitride nanotubes when interacting with nickel, titanium, palladium and gold metal atoms. These interactions occurred via adsorption, intercalation, nitrogen substitutional doping and boron substitutional doping. The wide band gaps intrinsic to the pristine boron nitride nanotubes were successfully tuned upon interaction with the metal atoms irrespective of the type of interactions. However, for most of the interactions that occurred via intercalation and nitrogen substitutional doping, the boron nitride nanotube was found to possess semi-metallic properties. More states were added in the density of states upon interaction in which the d orbital of the transition metal atoms was found to be the major contributor to the increase in density of states. 1. Introduction Following the first theoretical predictions of the existence of boron nitride nanotubes (BNNT) in 1994 [1–3] and the confirmation of its experimental synthesis a year after [4], BNNTs have sparked a lot of attention amongst the scientific community due to their myriad of elec- trical, thermal, mechanical and chemical properties [5]. Compared to carbon nanotube (CNT) which was discovered in 1991 [6], BNNTs possess much better electrical properties than CNTs and as such have recently been considered as possible alternatives for CNTs [7]. This is mainly due to the fact that the electrical properties of CNTs are depen- dent on their diameter and chirality [8]. This then poses a challenge when CNTs with desired electrical properties are to be separated from the others. Even though BNNTs has a similar geometric structure to CNTs, their electrical properties differ. CNTs are either of a metallic or semi conducting in nature, while BNNTs has an insulating characteristic; with a wide band gap range of 5.0–6.0 eV [1,2,9]. The wide band gap is as a result of a partial ionic character that exists between the boron-nitrogen bond due to the difference in electronegativity of the two elements [5, 10]. These wide band gaps have applications in the fields of nano- composites, biodegradable polymers and nanomedicine [3]. Although BNNTs has a wider band gap, extensive research suggests that interaction of metal atoms with BNNTs either by adsorption or doping with the aim of inducing impurity states within the band gap can significantly reduce the band gap, thereby allowing the BNNT to have semiconducting characteristics [11–15]. Such BNNTs could be promising materials in the nanoelectronics industry. Previous DFT calculations done using the four transition metals atoms (nickel, titanium, palladium and gold) to study their interactions with single-walled carbon nanotubes found that, gold atoms were able to change the electronic properties of the carbon nanotube irrespective of the site of interaction [16]. A cursory survey of literature reveals a gap in the study and under- standing of the interactions of BNNTs with these transition metals. Therefore, in this paper, we aim to present a detailed systematic study of doping, adsorption and intercalation of nickel, gold, palladium and ti- tanium interacting with BNNTs using density functional theory/local density approximation calculations (DFT/LDA) in order to shed light on their electronic properties which has application for nanoelectronics. 2. Model system Four different BNNT configurations, (3,3), (4,2), (5,2) and (6,0) were selected for this study due to similarity of their tube diameters. Details of the BNNT configurations used for this work are provided in Table 1 below. A total of sixteen (16) BNNTs were built for each of the 4 different configurations using the Virtual NanoLab (VNL 2017.1) software [17] * Corresponding author. E-mail address: ayaya@ug.edu.gh (A. Yaya). Contents lists available at ScienceDirect Results in Materials journal homepage: www.journals.elsevier.com/results-in-materials https://doi.org/10.1016/j.rinma.2019.100029 Received in revised form 30 August 2019; Accepted 13 September 2019 Available online 28 September 2019 2590-048X/© 2019 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by- nc-nd/4.0/). Results in Materials 2 (2019) 100029