Structure-dependent strength and toughness in dodecahedral silica nanocage
TY Hao and J Xu and ZM Hossain, JOURNAL OF APPLIED PHYSICS, 128, 064303 (2020).
Nanocages are structurally complex hollow low-dimensional materials that offer unique properties and functions that are inaccessible in bulk materials. They have tremendous potential in revolutionizing a number of fields including drug delivery and nanotechnology, but their applications remain limited primarily due to inadequate understanding of their extreme mechanical properties. Here, using reactive force field- based classical molecular dynamics simulations, we explore the bulk modulus, strength, and toughness modulus for a number of dodecahedral silica nanocages. The results show that, both under hydrostatic tension and compression, the mechanical properties vary nonlinearly with the structural parameters. Also, unlike bulk silica-which shows softening under tension in the nonlinear regime of mechanical deformation-silica nanocage exhibits stiffening at higher deformation that originates from the structural resistance of the nanocage. We show that the surface-area to volume ratio accurately describes the softening and stiffening behavior of the cage. Likewise, under compression, the nanocage shows three distinctive regimes: (i) linear decrease in stress with increasing strain, (ii) constant stress states with increasing strain representing shrinkage of the empty space, and (iii) exponential decrease in stress with increasing strain dominated by strong repulsion. These findings highlight the possibility of attaining a diverse set of mechanical properties from a nanocage by tailoring its structural parameters.
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