Multiresolution atomistic simulations of dynamic fracture in nanostructured ceramics and glasses

• Published in: International journal of fracture Vol. 121; no. 1-2; pp. 71 - 79
• Main Authors: KALIA, Rajiv K, NAKANO, Aiichiro, VASHISHTA, Priya, ROUNTREE, Cindy L, VAN BRUTZEL, Laurent, OGATA, Shuji
• Format: Conference Proceeding Journal Article
• Language: English
• Published: Heidelberg Springer 01.05.2003; Springer Nature B.V
• Subjects: Algorithms; Applied sciences; Building materials. Ceramics. Glasses; Ceramic industries; Ceramics; Chemical industry and chemicals; Chemical reactions; Coalescing; Computational techniques; Computer simulation; Condensed matter: structure, mechanical and thermal properties; Crack tips; Crossovers; Decomposition; Density functional theory; Dynamic structural analysis; Exact sciences and technology; Fatigue, brittleness, fracture, and cracks; Fracture surfaces; Fracture toughness; General studies; Glasses; Mathematical methods in physics; Meanders; Mechanical and acoustical properties of condensed matter; Mechanical properties of solids; Molecular dynamics; Morphology; Nanoparticles; Nanostructure; Organic chemistry; Parallel computers; Physics; Silicon dioxide; Silicon nitride; Simulation; Strain; Stress intensity factors; Technical ceramics; Water chemistry; glasses; Molecular dynamics; nanostructured ceramics; dynamic fracture
• ISSN: 0376-9429; 1573-2673
• DOI: 10.1023/a:1026216101073

Multimillion atom molecular-dynamics (MD) simulations are performed to investigate dynamic fracture in glasses and nanostructured ceramics. Using multiresolution algorithms, simulations are carried out for up to 70 ps on massively parallel computers. MD results in amorphous silica (a-SiO2) reveal the formation of nanoscale cavities ahead of the crack tip. With an increase in applied strain, these cavities grow and coalesce and their coalescence with the advancing crack causes fracture in the system. Recent AFM studies of glasses confirm this behavior. The MD value for the critical stress intensity factor of a-SiO2 is in good agreement with experiments. Molecular dynamics simulations are also performed for nanostructured silicon nitride (n-Si3N4). Structural correlations in n-Si3N4 reveal that interfacial regions between nanoparticles are amorphous. Under an external strain, nanoscale cavities nucleate and grow in interfacial regions while the crack meanders through these regions. The fracture toughness of n-Si3N4 is found to be six times larger than that of crystalline α-Si3N4. We also investigate the morphology of fracture surfaces. MD results reveal that fracture surfaces of n-Si3N4 are characterized by roughness exponents 0.58 below and 0.84 above a certain crossover length, which is of the order of the size of Si3N4 nanoparticles. Experiments on a variety of materials reveal this behavior. The final set of simulations deals with the interaction of water with a crack in strained silicon. These simulations couple MD with a quantum-mechanical (QM) method based on the density functional theory (DFT) so that chemical processes are included. For stress intensity factor K=0.4 MPa m1/2, we find that a decomposed water molecule becomes attached to dangling bonds at the crack or forms a Si-O-Si structure. At K=0.5 MPa m1/2, water molecules decompose to oxidize Si or break Si-Si bonds.