Computational studies on aluminum nitride and aluminum phosphide nanotubes: density functional calculations of 27Al electric field gradient tensors

Abstract  

Nuclear quadrupole resonance (NQR) parameters including the nuclear quadrupole coupling constant (C _Q) and asymmetry parameter (η _Q) at the sites of various ²⁷Al nuclei on (6,0) zigzag and (4,4) armchair AlN and AlP nanotubes (NTs) were calculated by using the density functional theory (DFT) method to study the properties of the electronic structures of the nanotubes. Geometry optimizations were carried out at the B3LYP/6-31G* level of theory using the Gaussian 03 suite of programs. The calculated electric field gradient tensors were converted to the nuclear quadrupole resonance parameters, C _Q constant, and η _Q parameter. The quadrupole resonance parameters in each of the structures were divided into four layers with equivalent electric field gradient tensor eigenvalues in each layer. The results show that, in AlN and AlP nanotubes, the Al atoms at the edges of the nanotubes play dominant roles in determining the electronic behavior of the nanotubes and important roles in growth and synthesis processes of the nanotubes. Also the average values of C _Q(²⁷Al) for the AlNNT models were higher in comparison with the AlPNT models, while variations of C _Q(²⁷Al) in AlPNTs were greater in comparison with in AlNNTs.