Molecular Dynamics Simulation of Shock Deformed Aluminum

poste

Isomorphic phase transformation in shocked cerium using molecular dynamics

Cerium (Ce) undergoes a significant (∼16%) volume collapse associated with an isomorphic fcc-fcc phase transformation when subject to compressive loading. We present here a new Embedded Atom Method (EAM) potential for Cerium that models two minima for the two fcc phases. We show results from its use in Molecular Dynamics (MD) simulations of Ce samples subjected to shocks with pressures ranging from 0.5 to 25 GPa. A split wave structure is observed, with an elastic precursor followed by a plastic wave. The plastic wave causes the expected fcc-fcc phase transformation. Comparisons to experiments and MD simulations on Cesium (Cs) indicate that three waves could be observed. The construction of the EAM potential may be the source of the difference

Isomorphic phase transformation in shocked Cerium using molecular dynamics

Cerium (Ce) undergoes a significant (∼16%) volume collapse associated with an isomorphic fcc-fcc phase transformation when subject to compressive loading. We present here a new Embedded Atom Method (EAM) potential for Cerium that models two minima for the two fcc phases. We show results from its use in Molecular Dynamics (MD) simulations of Ce samples subjected to shocks with pressures ranging from 0.5 to 25 GPa. A split wave structure is observed, with an elastic precursor followed by a plastic wave. The plastic wave causes the expected fcc-fcc phase transformation. Comparisons to experiments and MD simulations on Cesium (Cs) indicate that three waves could be observed. The construction of the EAM potential may be the source of the difference

Isomorphic phase transformation in shocked Cerium using molecular dynamics

Cerium (Ce) undergoes a significant (∼16%) volume collapse associated with an isomorphic fcc-fcc phase transformation when subject to compressive loading. We present here a new Embedded Atom Method (EAM) potential for Cerium that models two minima for the two fcc phases. We show results from its use in Molecular Dynamics (MD) simulations of Ce samples subjected to shocks with pressures ranging from 0.5 to 25 GPa. A split wave structure is observed, with an elastic precursor followed by a plastic wave. The plastic wave causes the expected fcc-fcc phase transformation. Comparisons to experiments and MD simulations on Cesium (Cs) indicate that three waves could be observed. The construction of the EAM potential may be the source of the difference

Large-scale molecular-dynamics study of the nucleation process of martensite in Fe-Ni alloys

High-performance large-scale molecular-dynamics (MD) simulations provide an atomistic insight of the nucleation process in Fe80Ni20. With the MD code SPaSM (Scalable Parallel Short-range Molecular Dynamics [1]) it is possible to follow the nucleation and further growth of the martensite structure (bcc) for more than one million atoms. The simulations show that the nucleation process is heterogeneous, at pre-existing defects. Further growth of the martensite structure into the austenite matrix (fcc) forms a typical twin structure on the nanoscale. Analysis of energy barriers between the martensite and the austenite can be used to interpret the nucleation process

Large-scale molecular dynamics simulations of particulate ejection and Richtmyer-Meshkov instability development in shocked copper

We present the results of recent large-scale, non-equilibrium molecular dynamics (NEMD) simulations of shock-induced surface instability development. We consider single crystal Cu described by an embedded atom method potential and driven by a shock wave along the [111] crystallographic direction, impinging upon a roughened Cu/vacuum or Cu/Ne interface. The NEMD simulation cell is a quasi-2D 2.23 μm×5.67 μm slab geometry, 1.5 nm thick in the (periodic) third dimension. The first third of the sample length (1.89 μm) is occupied by Cu (530 million atoms), and the remainder either empty vacuum or Ne gas (195 million atoms). The Cu/Ne (or Cu/vacuum) interface has an initial perturbation with average amplitude 30 nm and dominant wavelength of 0.74 μm. A shock wave is created by driving the front end of the Cu slab at a fixed particle velocity up = 2.0 to 3.5 km/s. Single-mode and multi-mode interfaces were considered using 212,992 CPUs of the LLNL BlueGene/L supercomputer for times on the order of 1 ns. The higher particle velocities studied here span shock Hugoniot and release states from solid to liquid, including the fluid-solid mixed phase