We report diffusive molecular dynamics simulations concerned with the lithiation of Si nano-pillars, i. e., nano-sized Si rods held at both ends by rigid supports. The duration of the lithiation process is of the order of miliseconds, well outside the range of molecular dynamics but readily accessible to diffusive molecular dynamics. The simulations predict an alloy Li 15 Si 4 at the fully lithiated phase, exceedingly large and transient volume increments up to 300% due to the weakening of Si-Si iterations, a crystalline-to-amorphous-tolithiation phase transition governed by interface kinetics, high misfit strains and residual stresses resulting in surface cracks and severe structural degradation in the form of extensive porosity, among other effects.

Thin, high-density layers of dopants in semiconductors, known as δ-layer systems, have recently attracted attention as a platform for exploration of the future quantum and classical computing when patterned in plane with atomic precision. However, there are many aspects of the conductive properties of these systems that are still unknown. Here we present an open-system quantum transport treatment to investigate the local density of electron states and the conductive properties of the δ-layer systems. A successful application of this treatment to phosphorous δ-layer in silicon both explains the origin of recently-observed shallow sub-bands and reproduces the sheet resistance values measured by different experimental groups. Further analysis reveals two main quantum-mechanical effects: 1) the existence of spatially distinct layers of free electrons with different average energies; 2) significant dependence of sheet resistance on the δ-layer thickness for a fixed sheet charge density.

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We present an open-system quantum-mechanical 3D real-space study of the conduction band structure and conductive properties of two semiconductor systems, interesting for their beyond-Moore and quantum computing applications: phosphorus $$\delta$$ δ -layers and P $$\delta$$ δ -layer tunnel junctions in silicon. In order to evaluate size quantization effects on the conductivity, we consider two principal cases: nanoscale finite-width structures, used in transistors, and infinitely-wide structures, electrical properties of which are typically known experimentally. For devices widths $$W<10$$ W < 10  nm, quantization effects are strong and it is shown that the number of propagating modes determines not only the conductivity, but the distinctive spatial distribution of the current-carrying electron states. For $$W>10$$ W > 10  nm, the quantization effects practically vanish and the conductivity tends to the infinitely-wide device values. For tunnel junctions, two distinct conductivity regimes are predicted due to the strong conduction band quantization.

We present a package to simulate long-term diffusive mass transport in systems with atomic scale resolution.The implemented framework is based on a non-equilibrium statistical thermo-chemo-mechanical formulation of atomic systems where effective transport rates are computed by using kinematic diffusion laws. Our implementation is built as an add-on to the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) code. It is compatible with other LAMMPS' functionalities, and shows a good parallel scalability and efficiency. In applications involving mass transport, our framework is able to simulate problems of technological interest for exceedingly large time scales using an atomistic description, which are not reachable with the state-of-the-art molecular dynamics techniques. To validate the implementation, we investigated vacancy diffusion, vacancy assisted dislocation climb in metals at high-temperatures, segregation of solutes in free surfaces, diffusion of solutes to grain boundaries, and Hydrogen diffusion in Palladium nanowires.These examples were validated against known theories, methodologies or experimental results when possible, showing good agreement in all cases.