Raman and infrared-active modes in MS2 nanotubes (M=Mo,W)

Abstract

Lattice dynamics of all the single-wall MS2 nanotubes with a diameter range of 1-20 nm is studied within full symmetry implemented valence-force-field model. Particularly, frequencies of infrared and Raman active modes are examined to clarify possible application of these methods in the experimental sample characterization. A prescription for experimental distinction of zig-zag, armchair and chiral tubes, based on their different symmetry and resulting selection rules, is proposed. Displacements significantly depend on the chiral angle only for two MoS2 modes, namely twisting in phase (rigid layer) and breathing out of phase, and none of WS2 modes. © 2006 The American Physical Society.