Magnetism of single-walled silicon carbide nanotubes doped by boron, nitrogen and oxygen Ahmed Maghnaoui, Ahmed Boufelfel n Laboratoire de Physique, Universite´ du 08 mai 45, BP 401, 24000 Guelma, Algeria article info Article history: Received 9 February 2012 Received in revised form 7 April 2012 Available online 24 April 2012 Keywords: SiC Nanotube Magnetic semiconductor DFT Band structure abstract We calculated, using spin polarized density functional theory, the electronic properties of zigzag (10,0) and armchair (6,6) semiconductor silicon carbide nanotubes (SiCNTs) doped once at the time with boron, nitrogen, and oxygen. We have looked at the two possible scenarios where the guest atom X (B, N, O), replaces the silicon X Si , or the carbon atom X C , in the unit cell. We found that in the case of one atom B @ SiCNT replacing a carbon atom position annotated by B C exhibits a magnetic moment of 1 m B / cell in both zigzag and armchair nanotubes. Also, B replacing Si, (B Si) , induce a magnetic moment of 0.46 m B /cell in the zigzag (10,0) but no magnetic moment in armchair (6,6). For N substitution; (N C ) and (N Si ) each case induce a magnetic moment of 1 m B /cell in armchair (6,6), while N Si give rise to 0.75 m B / cell in zigzag (10,0) and no magnetic moment for N C . In contrast the case of O C and O Si did not produce any net magnetic moment in both zigzag and armchair geometries. & 2012 Elsevier B.V. All rights reserved. 1. Introduction Silicon carbide nanotubes (SiCNTs) have been successfully synthesized by different groups [1–3]. Also, they have been investigated using ab initio density functional theory in details [4,5]. It was found that SiCNTs with alternating Si–C bonds are more stable than the ones which contain C–C or Si–Si bonds [4]. While carbon nanotubes (CNTs) have been found to be either metallic or semiconducting, depending on their diameter and chirality, these calculations show that all SiCNTs are semiconduc- tors. The energy band gap of the SiCNTs is dependent on their diameter and chirality, with direct gaps for zigzag tubes and indirect gaps for armchair and chiral tubes, and the band gap increases with increasing tube diameter. SiCNTs are considered to have advantages over CNTs because they may possess high reactivity of exterior surface facilitating to sidewall decoration and stability against oxidation in air at high temperature [5], which may have potential applications in nanoelectronics devices. Mpourmpakis et al. [6] have shown that the heteropolarity of the Si–C bonds results in a higher binding energy between hydrogen molecules and the nanotube walls, making SiCNTs a better choice than CNTs for hydrogen storage. Magnetic nanotubes (MNTs) are scientifically interesting and with many hopeful applications as materials of the future gen- erations of nanoelectronic devices in permanent magnetism, magnetic recording, and spintronics [7–9]. Various experimental [10,11] and theoretical [12,13] studies have explored the correla- tion between the defect and the magnetization in carbon nano- tubes CNTs. Also, boron nitrate nanotubes (BNNTs) [14] and magnesium oxide nanotubes (MgONTs) [15] have been investi- gated but to the best of our knowledge the case of induced magnetism in SiCNTs is not reported yet. In this paper, we report for the first time, using first principles calculations, the presence of magnetism in single wall SiCNTs when one atom of C or Si is replaced by B or N in the unit cell for the configurations zigzag (10,0) and armchair (6,6). 2. Methodology Our calculations are based on first principles density functional theory (DFT). Due to the important number of atoms used in the primitive cell, we judged that the adequate calculation scheme where a good compromise between accuracy and speed is the one implemented in the SIESTA code [16,17]. The code self-consis- tently solves the standard Kohn–Sham (KS) equations. For the exchange-correlation term we use local spin density approxima- tion (LSDA), as parametrized by Perdew and Zunger [18]. The valence electrons were described by normconserving Troullier– Martins pseudopotentials [19] in the Kleinman–Bylander factor- ized form [20,21]. Sankey and Niklewsky finite-range pseudo atomic orbitals (PAOs) [22] are utilized as the split-valence double zeta basis set with polarization (DZP) for the valence electrons. The charge densities were represented on a mesh with a Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/jmmm Journal of Magnetism and Magnetic Materials 0304-8853/$ - see front matter & 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jmmm.2012.04.003 n Corresponding author. Tel.: þ213 37 207795; fax: þ213 37 21 58 51. E-mail address: ahboufelfel@gmail.com (A. Boufelfel). Journal of Magnetism and Magnetic Materials 324 (2012) 2753–2760