Origins of structural and electronic transitions in disordered silicon
- 6 January 2021
- journal article
- research article
- Published by Springer Science and Business Media LLC in Nature
- Vol. 589 (7840), 59-64
- https://doi.org/10.1038/s41586-020-03072-z
Abstract
Structurally disordered materials pose fundamental questions1,2,3,4, including how different disordered phases (‘polyamorphs’) can coexist and transform from one phase to another5,6,7,8,9. Amorphous silicon has been extensively studied; it forms a fourfold-coordinated, covalent network at ambient conditions and much-higher-coordinated, metallic phases under pressure10,11,12. However, a detailed mechanistic understanding of the structural transitions in disordered silicon has been lacking, owing to the intrinsic limitations of even the most advanced experimental and computational techniques, for example, in terms of the system sizes accessible via simulation. Here we show how atomistic machine learning models trained on accurate quantum mechanical computations can help to describe liquid–amorphous and amorphous–amorphous transitions for a system of 100,000 atoms (ten-nanometre length scale), predicting structure, stability and electronic properties. Our simulations reveal a three-step transformation sequence for amorphous silicon under increasing external pressure. First, polyamorphic low- and high-density amorphous regions are found to coexist, rather than appearing sequentially. Then, we observe a structural collapse into a distinct very-high-density amorphous (VHDA) phase. Finally, our simulations indicate the transient nature of this VHDA phase: it rapidly nucleates crystallites, ultimately leading to the formation of a polycrystalline structure, consistent with experiments13,<a data-track="click" data-track-action="reference anchor"...Keywords
This publication has 88 references indexed in Scilit:
- Computer simulations of crystallization kinetics in amorphous silicon under pressureJournal of Applied Physics, 2012
- Nucleation mechanism for the direct graphite-to-diamond phase transitionNature Materials, 2011
- Pressure-induced crystallization of amorphous Ge2Sb2Te5Journal of Applied Physics, 2010
- The liquid-liquid phase transition in silicon revealed by snapshots of valence electronsProceedings of the National Academy of Sciences of the United States of America, 2010
- Ab initio molecular simulations with numeric atom-centered orbitalsComputer Physics Communications, 2009
- From ultrasoft pseudopotentials to the projector augmented-wave methodPhysical Review B, 1999
- Pressure-induced phase transition of crystalline and amorphous silicon and germanium at low temperaturesHigh Pressure Research, 1996
- Projector augmented-wave methodPhysical Review B, 1994
- Constant pressure molecular dynamics algorithmsThe Journal of Chemical Physics, 1994
- High pressure superconductivity of siliconPhysica B+C, 1985