Computer simulation of local order in condensed phases of silicon

TLDR

The authors propose a two‑ and three‑body potential‑energy function to model interactions in solid and liquid silicon. They test this potential by running 216‑atom periodic‑boundary molecular‑dynamics simulations. Simulations show that heating the diamond crystal causes spontaneous melting into a liquid that structurally matches real silicon, revealing a temperature‑independent inherent structure and suggesting that both melting and freezing can be described by critical mean displacements from potential minima.

Abstract

A model potential-energy function comprising both two- and three-atom contributions is proposed to describe interactions in solid and liquid forms of Si. Implications of this potential are then explored by molecular-dynamics computer simulation, using 216 atoms with periodic boundary conditions. Starting with the diamond-structure crystal at low temperature, heating causes spontaneous nucleation and melting. The resulting liquid structurally resembles the real Si melt. By carrying out steepest-descent mappings of system configurations onto potential-energy minima, two main conclusions emerge: (1) a temperature-independent inherent structure underlies the liquid phase, just as for ``simple'' liquids with only pair interactions; (2) the Lindemann melting criterion for the crystal apparently can be supplemented by a freezing criterion for the liquid, where both involve critical values of appropriately defined mean displacements from potential minima.