Structural stability of a coaxial carbon nanotube inside a boron-nitride nanotube

The structural stability of a coaxial carbon nanotube inside a boron-nitride nanotube (C@BNNT) is investigated by molecular dynamics simulation. The geometric structures of armchair C(5,5)@BN(n,n) and zigzag C(9,0)@BN(m,0) nanotubes (n = 8-15; m = 15-22) are optimized by the density functional theory method using the DMol3 code. A comparison of the variation in the tube radius and analyses of the bind energy and radial distribution function show that the best BN(n,n) nanotubes for coupling with C(5,5) to form C(5,5)@BN(n,n) are BN(10,10), and the best BN(m,0) nanotubes for coupling with C(9,0) to form C(9,0)@BN(m,0) are BN(17,0) and BN(18,0). The optimal interwall distances between the inner C tube and the outer BN tube are about 0.35 nm for armchair and from 0.33 to 0.36 nm for zigzag nanotubes, respectively. The armchair C@BNNTs achieve a more stable combination structure than the zigzag case. Analyses of their energy and deformation electron density reveal that the interwall interaction between the inner carbon nanotube and outer boron-nitride nanotube is a van der Waals interaction. (C) 2010 Elsevier Ltd. All rights reserved.