Computational studies of effects of tubular lengths on the NMR properties of pristine and carbon decorated boron phosphide nanotubes Mahmoud Mirzaei a, * , Masoumeh Meskinfam b a Department of Nanotechnology, Pharmaceutical Sciences Branch, Islamic Azad University, Tehran, Iran b Department of Chemistry, Lahijan Branch, Islamic Azad University, Lahijan, Iran article info Article history: Received 3 June 2011 Accepted 12 August 2011 Available online xxx Keywords: Density functional theory Boron phosphide Nanotube Nuclear magnetic resonance abstract Density functional theory (DFT) calculations were performed to investigate the effects of tubular lengths on the nuclear magnetic resonance (NMR) properties of boron phosphide (BP) nanotubes. To this aim, the properties of pristine and carbon decorated (C-decorated) models of representative zigzag and armchair BP nanotubes were investigated. The results indicated that the atoms at the edges of nanotubes do not detect any significant changes. The NMR properties of boron atoms only detect slight changes but those of phosphorous atoms are more notable. Ó 2011 Elsevier Masson SAS. All rights reserved. 1. Introduction Due to the complexity of controlling semiconducting or metallic properties of carbon nanotubes (CNTs) during their synthesis [1], considerable efforts have been performed to introducing other kinds of nanotubes consisting of other atoms of the periodic table of elements [2]. In this case, the counterparts of atoms of the third (III) and fifth (V) groups of the periodic table of elements have been proposed as possible substitutions for the CNTs [3]. Further studies have also indicated that the IIIeV nanotubes always exhibit semi- conducting properties independent of their structural topologies [4]. Moreover, due to differences of the values of electronegativities, the IIIeV nanotubes also show ionic properties, which could make their dispersion in water much easier than the non-ionic and hydrophobic CNTs. Indeed, dispersing the nanotubes in the hydrated systems is very important in determining their applica- tions, especially in the poly hydrated biological systems [5]. The existence and properties of tubular structures of IIIeV counterparts (III: boron, aluminum, and gallium; V: nitrogen, phosphorous, and arsenic) have been investigated by earlier computational and experimental works [6e12]. The studies have also indicated that the properties of IIIeV nanotubes are influenced by the presence of impurities during their synthesis, in which the carbon atoms are viewed as common impurities in the synthesizing environments [13e15]. Among the important techniques of structural investigations, nuclear magnetic resonance (NMR) spectroscopy stands as an insightful technique for investigating the properties of matters in the solid phases [16]. Chemical shielding (CS) tensors are elements of NMR technique, which are originated from the electronic sites of the dipolar nuclei such as boron-11 ( 11 B) and phosphorous-31 ( 31 P). The CS tensors are very sensitive to the electronic densities around the nuclei and they detect any perturbations to the environments of these sites [16]. The NMR parameters including isotropic and anisotropic CS parameters could be well obtained by either quantum chemical calculations or experimental measurements [17]. Earlier investigations have indicated that the computed NMR parameters could reveal insightful trends about the properties of nanotubes [18e21]. However, due to the complexity of electronic structures of nanotubes, performing experimental NMR measure- ments for nanotubes is almost a formidable task [18]. Hereby, the high level computations of NMR parameters could play a dominant role in further investigating the properties of nanotubes. In this work, we have investigated the influences of tubular lengths on the NMR parameters of boron phosphide (BP) nano- tubes. To achieve our purposes of study, we have considered various lengths of pristine and carbon decorated (C-decorated) models of (6,0) and (4,4) BP nanotubes as representatives of zigzag and armchair nanotubes. We have allowed the geometries of all atoms of the investigated structures to relax during the optimiza- tion process. Subsequently, we have evaluated the NMR parameters for the optimized models of BP nanotubes. Earlier studies have indicated that the atoms of IIIeV nanotubes close to the C- * Corresponding author. Tel.: þ98 912 8117305. E-mail address: mdmirzaei@iaups.ac.ir (M. Mirzaei). Contents lists available at SciVerse ScienceDirect Solid State Sciences journal homepage: www.elsevier.com/locate/ssscie 1293-2558/$ e see front matter Ó 2011 Elsevier Masson SAS. All rights reserved. doi:10.1016/j.solidstatesciences.2011.08.018 Solid State Sciences xxx (2011) 1e5 Please cite this article in press as: M. Mirzaei, M. Meskinfam, Computational studies of effects of tubular lengths on the NMR properties of pristine and carbon decorated boron phosphide nanotubes, Solid State Sciences (2011), doi:10.1016/j.solidstatesciences.2011.08.018