Atomistic study of the (001), 90 degrees twist boundary in silicon

摘要

A new type of a structural unit (the <(4)over bar 2m> dreidl) is proposed on the basis of molecular dynamics simulations for the core model of the (001), 90 degrees twist grain boundary in silicon. The structural unit resembles a polyhedron in which some edges, not corresponding to bonds between atoms, are absent. The dreidl has the <(4)over bar 2m> (D-2d) point-group symmetry and consists of 14 atoms which form eight five-membered rings maintaining tetrahedral bonding in the boundary core. Molecular dynamics simulations with the empirical Tersoff-potential were performed to evaluate the energy of the (001), 90 degrees twist boundary at T = 0 K. The effect of both rigid-body translations parallel to the grain boundary plane and alternative reconstructions involving conventional structural units was investigated. Despite the high degree of dimerization the twist boundary was found to have a low energy compared with structural models of twist grain boundaries in silicon previously studied. [References: 30]