We investigate the bending flexibility of carbon nanotubes (CNTs) with encapsulated C60 fullerenes, using molecular dynamics (MD) simulations. Our simulations on the bending of the fully ((C60)12@(10,10)) and partially ((C60)10@(10,10)) filled peapods show an 18 and 6.3% increase of the flexural rigidity, and a 45 and 11% increase of the buckling strength, respectively, compared to the empty (10, 10) CNT. What is characteristically different for the peapod from the empty CNT is the presence of a transitional region in the loading process that proceeds to the onset of buckling. Within this transitional region, the interaction between the encapsulated fullerenes and the hosting CNT leads to an unusual configuration of the peapod, in which there are ripples along the inner arc of the bent peapod. The transition region in the partially filled peapod is short compared with the fully filled peapod. This is mainly caused by the axial motion of C60 fullerenes, especially after the appearance of the small ripple. The rippling configuration has been reported previously in the bending of multi-walled CNTs, where it emerges after the critical bending angle. However, in the present case, the peapod remains perfectly elastic in this transitional region until buckling takes place.

Recently, a series of graphene-like binary monolayers (g-SiC ), where Si partly substitutes the C positions in graphene, have been obtained by tailoring the band gaps of graphene and silicene that have made them a promising material for application in opto-electronic devices. Subsequently, evaluating the mechanical properties of g-SiC has assumed great importance for engineering applications. In this study, we quantified the in-plane mechanical properties of g-SiC (x = 7, 5, 3, 2 and 1) monolayers (also including graphene and silicene) based on density function theory. It was found that the mechanical parameters of g-SiC , such as the ideal strength, Young's modulus, shear modulus, Poisson's ratio, as well as fracture toughness, are overall related to the ratio of Si-C to C-C bonds, which varies with Si concentration. However, for g-SiC and g-SiC, the mechanical properties seem to depend on the structure because in g-SiC, the C-C bond strength is severely weakened by abnormal stretching, and in g-SiC, conjugation structure is formed. The microscopic failure of g-SiC exhibits diverse styles depending on the more complex structural deformation modes introduced by Si substitution. We elaborated the structure-properties relationship of g-SiC during the failure process, and in particular, found that the structural transformation of g-SiC and g-SiC is due to the singular symmetry of their structure. Due to the homogeneous phase, all the g-SiC investigated in this study preserve rigorous isotropic Young's moduli and Poisson's ratios. With versatile mechanical performances, the family of g-SiC may facilitate the design of advanced two-dimensional materials to meet the needs for practical mechanical engineering applications. The results offer a fundamental understanding of the mechanical behaviors of g-SiC monolayers.

Molecular dynamics was used to study the effects of He-doping on brittle fracture in Ni. It was found that the released strain energy during crack propagation with He-doping (Er) is higher than that without He-doping (Er0). Enhancement of the strain energy due to He-doping contributes to a driving force to promote crack growth. This indicates that doping of He clusters in Ni favors crack growth, particularly for He clusters with high He-to-vacancy ratios, in which strong He–Ni interaction plays an important role. Furthermore, Er decreases non-linearly with increasing distance of He clusters away from the crack tip. Our results show that embrittlement of the materials will be enhanced when either the He concentration or the fracture density is above a critical value. The effect of critical He concentration on embrittlement of the materials has been reported in experimental studies.