Atomistic analysis of 3D fracture fingerprints of mono- and bi- crystalline diamond and gold nanostructures

F Molaei and AH Mashhadzadeh and C Spitas and MR Saeb, ENGINEERING FRACTURE MECHANICS, 263, 108291 (2022).

DOI: 10.1016/j.engfracmech.2022.108291

Gold and diamond are elements of advanced systems. Considering covalent and ionic character of gold versus completely covalent structure of diamond, visualization of fracture behavior of their nanocrystalline structures is the key to understanding their mechanical stability in order to smoothen manufacturing advanced nano-devices. Nevertheless, 3D patterns of their fracture are rarely investigated. In this work, we compare the mechanical properties of (1 1 1) diamond and (100) gold from molecular dynamics (MD) simulations perspective. The effects of the temperature, grain boundary, and pre-cracking on the Young's modulus, fracture stress, fracture strain, and stress-strain behavior are investigated. Overall, failure in diamond occurred along certain low- energy cleavage planes, as per a brittle fracture mode with no plastic deformation. Moreover, no significant reduction was detected in the fracture strength of diamond upon temperature rise up to 800 K; but at 1000 K it decreased by 10%., unlike 34% drop computed for gold. Compared to ideally perfect monocrystalline structure, the fracture strength and Young's modulus of the bicrystalline gold decreased by 60% and 8%, respectively. Moreover, the average maximal tensile stress was severely dependent on the strain magnitude. For the diamond, however, the tensile strength decreased about 31-38% depending on the crack initiation pattern, while Young's modulus decreased by nearly 24%. In the presence of defects, the maximal fracture stress of diamond and gold experienced a reduction by 33% and 54%, respectively.

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