Superlattices and Microstructures 146 (2020) 106674 Available online 4 August 2020 0749-6036/© 2020 Elsevier Ltd. All rights reserved. Crack velocities and microstructural investigations in nickel nanowires with crack, crack-defect under mode-I and bending using large-scale molecular dynamics simulations Krishna Chaitanya Katakam , Natraj Yedla * Computational Materials Engineering Group, Department of Metallurgical and Materials Engineering, National Institute of Technology Rourkela, 769008, India A R T I C L E INFO Keywords: Molecular dynamics Crack-void Velocity Orientation Deformation ABSTRACT Crack propagation and crack-defect (void) interactions are investigated in nickel nanowires (NWs) of [010], [1-10], and [111] axial crystallographic orientations by subjecting to tensile loading (mode-I) at a temperature of 10 K and strain rate of 10 9 s -1 . From the molecular dynamic (MD) simulation results, it is observed that crack does not propagate in the [111] orientation NW. The crack velocity is 313 m/s in [010] orientation nickel NW with crack. The predominant deformation mechanisms are slip by Shockley partial dislocation in [010], [111] orientations, and twinning in [1-10] orientation. With the decrease in crack-void spacing from 20 Å to 5 Å, the average crack velocities (207 m/s-120 m/s) decrease in [010] orientation due to crack tip blunting arising from the crack-void coalescence. Three point bending simulations studies carried out on the above mentioned NWs also show similar deformation mechanism features and a decrease in crack velocities from 130 m/s-77 m/s. 1. Introduction Crack propagation, deformation behavior, and deformation mechanisms in single-crystal metals are strongly dependent on the atomic structure and lattice orientation [1–4]. Crack propagation in materials occurs by breaking of bonds between atoms [5], and in single crystals, it is related to slip or dislocation motion due to the absence of grain boundaries [1,4,6]. Crack propagation in materials is a multi-scale phenomenon, as seen above. It has been studied by several continuum models such as extended fnite element method (XFEM), crystal plasticity fnite element method (CPFEM), and numerical manifold method (NMM) [6]. However, these methods do not give insights into atomic-level details of fracture. So, atomistic models and simulations are needed to develop new materials. Molecular dynamics (MD) is a computational simulation tool that has been used in several studies to investigate the fracture and deformation mechanism at the atomic scale [1–3,6]. Studies on crack propagation in single crystal nickel show that crack growth is insignifcant in [111] orientation than in [110] and [100] orientations [7] due to crack tip blunting and formation of slip bands ahead of the crack tip. Zhang and Ghosh [4] studies also report that there is no crack growth in the single crystal nickel of [111] orientation till a strain of 2% and beyond this point, crack length decreases as the crack opening increases. Crack propagation studies in (010) twist boundary nickel bi-crystal flms show that crack propagation is hindered at 0 ◦ twist angle, at higher angles, new cracks initiate at grain boundaries that lead to the fracture [6,8]. * Corresponding author. E-mail address: yedlan@nitrkl.ac.in (N. Yedla). Contents lists available at ScienceDirect Superlattices and Microstructures journal homepage: www.elsevier.com/locate/superlattices https://doi.org/10.1016/j.spmi.2020.106674 Received 13 April 2020; Received in revised form 7 July 2020; Accepted 31 July 2020