Islamic Azad University at Shahr Rey

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Mirzaei M.,Islamic Azad University at Shahr Rey | Giahi M.,Islamic Azad University at Lahijan
Physica E: Low-Dimensional Systems and Nanostructures | Year: 2010

We have performed density functional theory (DFT) calculations employing BLYP exchange functional and 6-31 G* standard basis set by GAUSSIAN 98 package of program. The electronic structure properties of representative zigzag and armchair models of boron nitride nanotube (BNNT) and boron phosphide nanotube (BPNT) have been studied. The (6,0) and (4,4) structures have been optimized and the electric field gradient (EFG) tensors have been calculated at the sites of various boron-11 nuclei. The calculated EFG tensors have been converted to the equivalent experimental nuclear quadrupole resonance (NQR) parameters, quadrupole coupling constant and asymmetry parameter. The results revealed that the boron atoms at the edges of nanotubes play dominant roles in determining the electronic behaviors of BNNT and BPNT. The average of the calculated values of quadrupole coupling constants at the sites of boron-11 nuclei is in good agreement with experiments. © 2010 Elsevier B.V. All rights reserved.


Mirzaei M.,Islamic Azad University at Shahr Rey
Physica E: Low-Dimensional Systems and Nanostructures | Year: 2010

NMR parameters consisting of isotropic and anisotropic chemical shielding parameters have been calculated based on density functional theory (DFT) to investigate the properties of the electronic structures of the silicon-carbon (SiC) doped boron nitride nanotubes (BNNTs). The structures have been allowed to relax by performing all atomic optimization. Afterwards, the chemical shielding (CS) parameters have been calculated for the B-11, C-13, N-15, and Si-29 atoms in the pristine and the SiC-doped models of the (4,4) armchair and (6,0) zigzag BNNTs. The results indicated that the doping of the B and N atoms by the C and Si atoms, respectively, has more significant influence on the calculated NMR parameters than the doping of the B and N atoms by the Si and C atoms, respectively. In comparison to the pristine model, the band gaps detect more changes in the former model of the doping process. © 2010 Elsevier B.V. All rights reserved.


Mirzaei M.,Islamic Azad University at Shahr Rey | Giahi M.,Islamic Azad University at Lahijan
Physica B: Condensed Matter | Year: 2010

The electronic and structural properties of ultra small-diameter (3,0) and (4,0) zigzag and (2,2) and (3,3) armchair models of boron nitride nanotubes (BNNTs) are investigated by density functional theory (DFT) calculations. The atomic geometries of the considered models are optimized and then the electric field gradient (EFG) tensors are calculated at the sites of boron-11 and nitrogen-14 nuclei in the optimized structures. The results indicate that the small-diameter boron nitride nanotubes are proper for contributing to intermolecular interactions whereas the zigzag models are more preferred rather than the armchair ones. Furthermore, the boron-11 nuclei play dominant roles in the characterization of the electronic and structural properties of the BNNTs. The DFT calculations are performed by the GAUSSIAN 98 package. © 2010 Elsevier B.V. All rights reserved.


Mirzaei M.,Islamic Azad University at South Tehran | Mirzaei M.,Islamic Azad University at Shahr Rey
Solid State Sciences | Year: 2011

Density functional theory (DFT) calculations were performed to investigate carbon-doped (C-doped) models of representative structures of (6,0) zigzag and (4,4) armchair aluminum phosphide nanotube (AlPNT). To this aim, the structures of the C-doped models were optimized and chemical shielding (CS) parameters were subsequently calculated for the 13C, 27Al and 31P atoms of the optimized structures. Formation energies indicate that C-doping of P atom could be more favorable than C-doping of Al atom in both zigzag and armchair AlPNTs. Gap energies and dipole moments detected the effects of dopant; however, bond distances and tip diameters did not detect any changes in the C-doped models. The CS values for the Al and P atoms which were contributed to the Al-C and C-P bonds detected the significant changes and the slight changes were also observed for those atoms close to the C-doped region. The C atom played different roles in the C-doped models in which the tendency of C atom for contribution to the Al-C bond was lower than this tendency for contribution to the C-P bond. © 2010 Elsevier Masson SAS. All rights reserved.


Mirzaei M.,Islamic Azad University at Shahr Rey
Monatshefte fur Chemie | Year: 2010

Density-functional theory calculations have been performed to investigate the properties of the electronic structures of silicon-carbon-doped boron nitride nanotubes (BNNTs). The geometries of zigzag and armchair BNNTs were initially optimized and the quadrupole coupling constants subsequently calculated. The results indicate that doping of B and N atoms by C and Si atoms has more influence on the electronic structure of the BNNTs than does doping of B and N atoms by Si and C atoms. The changes of the electronic sites of the N atoms are also more significant than those of the B atoms. © Springer-Verlag 2010.


Mirzaei M.,Islamic Azad University at South Tehran | Miirzaei M.,Islamic Azad University at Shahr Rey
Solid State Communications | Year: 2010

We have performed density functional theory (DFT) calculations to investigate the properties of the electronic structure of the oxygen (O) terminated zigzag boron nitride nanotubes (BNNTs). To this end, the atoms of the tips of the representative (6, 0) BNNT are doped by the O atoms. Electric field gradient (EFG) tensors have been calculated in different models of the investigated BNNT and converted to quadrupole coupling constants (Χ) for B-11, N-14 and O-17 atoms. Our results indicated that the influence of O-termination on the properties of the electronic structure of the (6, 0) BNNT could be detected by the values of Χ parameters. These values revealed that the strength of N-O bonds could be weaker than B-O ones. © 2010 Elsevier Ltd. All rights reserved.


Mirzaei M.,Islamic Azad University at Shahr Rey
Zeitschrift fur Naturforschung - Section A Journal of Physical Sciences | Year: 2010

Structural properties of two representative (4,4) armchair and (6,0) zigzag boron phosphide nanotubes (BP-NTss) are studied by density functional theory (DFT) calculations. To this aim, both structures and also the equivalent layer-like structures are individually optimized; afterwards, the boron-11 and phosphorous-31 chemical shielding (CS) tensors are calculated in the optimized structures. The calculated energies indicate that tubular structures are stabilized and the CS tensors are divided into some layers based on equality of electronic properties in the structures. All computations are performed by Gaussian 98 program package. © 2010 Verlag der Zeitschrift für Naturforschung, Tübingen.


Mirzaei M.,Islamic Azad University at South Tehran | Mirzaei M.,Islamic Azad University at Shahr Rey
Journal of Molecular Structure: THEOCHEM | Year: 2010

The properties of boron (B)-doped models of representative (4,. 4) armchair and (6,. 0) zigzag silicon carbide nanotubes were investigated by density functional theory (DFT) calculations of chemical shielding (CS) parameters. The calculated results indicated that by B-doping of Si atom of armchair SiCNT, the CS parameters of C atoms only detect the effects but by B-doping of C atom, the CS parameters of both Si and C atoms detect the effects of doping. The CS parameters of both Si and C atoms detect notable changes by B-doping of either Si or C atoms of zigzag SiCNT. The role of electron receptor of B atom was more significant for the structure of (6,. 0) SiCNT in which C atom is doped by B atom. © 2010 Elsevier B.V.


Mirzaei M.,Islamic Azad University at South Tehran | Mirzaei M.,Islamic Azad University at Shahr Rey
Journal of Molecular Structure: THEOCHEM | Year: 2010

Electronic structures of two representative armchair and zigzag models of aluminum phosphide nanotube (AlPNT) were investigated by density functional theory (DFT) calculation of chemical shielding (CS) parameters of Al-27 and P-31 atoms. The optimized Al-P bond length was identical for both models. The diameters of both ends of the armchair model were identical whereas the diameter of P-end was much wider than Al-end of the zigzag model. The isotropic and anisotropic CS parameters were divided into layers based on detecting of similar electronic environments by the atomic sites of each layer. For the armchair model, the strength of Al-P bond at the end of nanotube was weaker than the body of nanotube whereas this trend was observed only for the P-end of the zigzag model. © 2010 Elsevier B.V.


Mirzaei M.,Islamic Azad University at Shahr Rey | Nouri A.,Islamic Azad University
Journal of Molecular Structure: THEOCHEM | Year: 2010

We have investigated the properties of the electronic structure of the aluminum doped (Al-doped) boron nitride nanotubes (BNNTs) by density functional theory (DFT) calculations. The structures are allowed to relax by performing all atomic optimization. Afterwards, the chemical shielding (CS) tensors are calculated for B-11, N-15, and Al-27 nuclei in the Al-doped forms and also pristine models of the (4,4) armchair and (6,0) zigzag BNNTs. The results indicated that the doping of B atom by Al atom, the properties of the electronic structure were less influenced regarding to the pristine model than the case of doping of N atom by Al atom. Furthermore, doping of N atom by Al atom yields the equivalent calculated values of the band gaps for the Al-doped forms of the armchair and zigzag models of BNNTs. © 2009 Elsevier B.V. All rights reserved.

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