Molecular dynamics simulation on deformation mechanisms in body-centered-cubic molybdenum nanowires

A systematic study on the deformation mechanisms of molybdenum (Mo) nanowires (NWs) was conducted using molecular dynamics simulations. Both axial orientation and wire thickness were found to play important roles in determining the deformation pathways. In the NWs with orientation 110/{111}, full dislocation plasticity is referentially activated on {110} planes. For both 100/{110} and 100/{100} NWs, twinning is the dominant mechanism with {112} being the coherent twin boundaries. A progressive slip process leads to a uniform elongation of 41 and the 100 wire axis reorients to 110. For 100/{100} NWs, the reorientation mechanism ceases to operate when the diameter d < 1 nm or d > 8 nm. The atomic chains are energetically preferred for ultrathin NWs after yielding due to the resemblance of the surface to the close-packed bcc planes, while multiple slip systems tend to be activated for larger NWs. Finally, a theoretical model is proposed to explain the underlying mechanism of size dependence of the yield stress.