doi: 10.1111/j.1460-2695.2006.01037.x Atomistic simulation of tensile strength and toughness of cracked Cu nanowires A. LUQUE, J. ALDAZABAL, J. M. MART ´ INEZ-ESNAOLA and J. GIL SEVILLANO CEIT and TECNUN (University of Navarra), P. Manuel Lardiz´ abal 15, 20018 San Sebasti´ an, Spain Received in final form 3 May 2006 ABSTRACT Virtual tensile experiments on cylindrical copper wires of nanometric diameter were car- ried out using molecular dynamics techniques based on the embedded-atom method. Transverse, atomically sharp surface cracks with circular fronts of different depths are introduced to evaluate their effect on the mechanical strength of the nanowires. The ax- isymmetric z-axis of the specimen is on the 001 direction of the nanowires. The analysis showsthat,at0K,thecrackedCunanowiresbehaveinaductilemanner,theirstrengthbe- ing determined by dislocation or twinning nucleation from the crack tip. Their calculated fracture toughness ranges from 0.6 to 3 MPa √ m. Keywords atomistic simulations; mechanical properties; micromechanical modelling; molecular dynamics; nanowires; toughness. NOMENCLATURE a = crack depth a, b = semi-axes of the elliptical crack front C ij = coefficients for computation of stress intensity factors D c = diameter of the nanowire E = Young’smodulus E i = energy of the ith atom f = coefficient depending on the elastic properties of the material F = embedding potential K I , K II = stress intensity factor (mode I and mode II) K c = toughness L 0 = initial length of the nanowire r = distance to the crack tip r ij = distance between atoms i and j u 1 ,u 2 = atomic displacements along the axes 1 and 2 of the crack V = pair potential Y = shape factor u = atomic displacement relative to the displacement of the crack tip θ = angle between the radial coordinate r and the crack plane ν = Poisson’s ratio ρ = electronic density ρ t = normalised total electronic density σ = nominal tensile stress σ max = maximum nominal (remote) tensile stress Correspondence: J. Gil Sevillano. E-mail: jgil@ceit.es INTRODUCTION Whiskers, used as composite reinforcing materials due to their high mechanical performance, are single crys- talline almost perfect fibres of nanometric transverse size. c  2006 The Authors. Journal compilation c  2006 Blackwell Publishing Ltd. Fatigue Fract Engng Mater Struct 29, 615–622 615