Strain dependent G-band mode frequency of single-walled carbon nanotubes

Based on a nonlinear stick-spiral model, we propose an analytical method to study the strain dependent G-band mode frequency of single-walled carbon nanotubes (SWCNTs) under axial, radial and torsional strain. The present method gives a direct connection between the G-band mode frequency and the external strain. It is shown that G-band mode frequency of a SWCNT is linearly dependent on strain when the strain is small, showing the possibility of using SWCNTs as strain sensors. However, significant nonlinearity may appear under larger strain. The G-band frequency depends also on the diameter and chirality of SWCNTs. More interestingly, it is shown that the vibrating direction of atoms may suddenly change under external strain, inducing a sudden transition between G-band modes (from A1g to E1g or inversely). (C) 2011 Elsevier Ltd. All rights reserved.