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Based on a molecular mechanics coupled with atomistic-based continuum theory, a closed-form formula is presented to examine the elastic properties of single- and double-walled carbon nanotubes subjected to hydrostatic pressure. Following the present model, the effects of the armchair and zigzag CNT structures on the pressure behavior are theoretically investigated. The computational result indicates that the bulk modulus is less sensitive to the chiral structures except for very small tube diameters. Moreover, closed-end nanotubes under hydrostatic pressure exhibit a larger bulking modulus than open ended nanotubes. The cap of the zigzag tubes has a larger effect on the bulk modulus when compared to the armchair tubes, especially in small diameter nanotubes. The predicted strain and the bulk modulus are in good agreement with existing theoretical results. [ABSTRACT FROM AUTHOR]

Abstract: In situ Raman scattering measurements of pristine and fluorinated double-walled carbon nanotube samples under high pressure have been performed. Due to the mechanical shielding effect of the outer tubes of the double-walls to the applied pressure, the Raman scattering lines from the inner tubes of both samples remained to be observed even at high pressure. [Copyright &y& Elsevier]