Dariusz Chrobak | Searcharxiv

arXiv2023

Crystal structure discrimination based on a single atom speed dynamics

Atom arrangement plays a critical role in determining material properties. It is, therefore, essential for materials science and engineering to identify and characterize distinct atom configurations. Currently, crystal structures can be determined either by its static properties or by quantifying its structural evolution. Here we show how to classify an atom into phase solely by its speed dynamics. We model silicon crystals at different phase transition points and use a single atom speed trajectory to demonstrate that crystal-structure-independent Maxwell distribution of speed is generated by crystal-structure-dependent atom dynamics. As the classification accuracy of the method increases with trajectory length, we show that subtle difference in local atomic structures can be identified using sufficiently long trajectories. Thanks to symbolization of atom dynamics, the method is computationally efficient and suitable for an analysis of large datasets on the fly.

cond-mat.mtrl-sci↗

arXiv2022

Comprehensive structural changes in nanoscale-deformed silicon modelled with an integrated atomic potential

In spite of remarkable developments in the field of advanced materials, silicon remains one of the foremost semiconductors of the day. Of enduring relevance to science and technology is silicon's nanomechanical behaviour including phase transformation, amorphization and dislocations generation, particularly in the context of molecular dynamics and materials research. So far, comprehensive modelling of the whole cycle of events in silicon during nanoscale deformation has not been possible, however, due to the limitations inherent in the existing interatomic potentials. This paper examines how well an unconventional combination of two well-known potentials - the Tersoff and Stillinger-Weber - can perform in simulating that complexity. Our model indicates that an irreversible deformation of silicon (Si-I) is set in motion by a transformation to a non-diamond structure (Si-nd), and followed by a subsequent transition to the Si-II and Si-XII' phases (Si-I->Si-nd->Si-II->Si-XII'). This leads to the generation of dislocations spreading outwards from the incubation zone. In effect, our simulations parallel each and every one of the structural changes detected experimentally in the deformed material. This includes both the sequence of phase transitions and dislocation activity, which - taken together - neither the Tersoff nor Stillinger-Weber, or indeed any other available Si interatomic potential, is able to achieve in its own right. We have sought to additionally validate our method of merging atomic potentials by applying it to germanium, and found it can equally well predict germanium's transformation from a liquid to amorphous state.

cond-mat.mtrl-sci↗