Onset of failure in argon by the effect of a shockwave: A molecular dynamics study

Molecular dynamic simulations of shockwaves in solid argon were performed. The simulation cell contains 51,840 atoms at 5 K interacting by means of a pairwise potential. The shockwave itself was introduced explicitly in the simulation by a piston hitting the sample from one side of the simulation box, at speeds ranging from 1.2 to 1.3 times the speed of sound in solid argon at the chosen density. In order to characterize the sample in terms of both structural and dynamic properties, we determine the density and temperature profiles according the advance of the shockwave, evaluating, for different slabs, the pair-distribution function, coordination number as well as performing a common neighbor analysis for the atoms. Our simulations reproduce the experimental Hugoniot curve and show how the material is break due to rarefaction waves. The picture that emerges is that when the shockwave starts, a local melting is produced in a region of the sample. Then, as the shockwave travels through the sample, a high density disordered phase is identified. When the piston stops, a rarefaction wave develops, producing a large tensile stress, which finally causes the failure of the sample.