Molecular Dynamics simulations of stress propagation and dislocations in crystals: example of Fe-Ni-Cr steel.

Simulations in molecular dynamics (MD) often are carried out in an applied pressure, as for instance in case of modelling the dynamics of dislocations in materials. In analysis of results a crucial role is played by the proper understanding of underlying process of pressure penetration itself, since this is a dynamic process occurring at the same time scales as the studied properties of material.

Movement of line dislocations in FCC steel 310S is found to depend on the size of nanometer sized structures. The effect is attributed to time (and size) dependencies of pressure propagation into the medium. The observation is crucial in interpreting any MD studies of pressure effects since these are governed by time-dependent internal virial stresses. In particular, velocity of dislocations scales better with value of local internal shear component of virial stress than with external shear pressure applied.