We study the conversion of bulk Se and Te, consisting of intertwined a helices, to structurally very dissimilar, atomically thin two-dimensional (2D) layers of these elements. Our ab initio calculations reveal that previously unknown and unusually stable \delta - and \eta-2D allotropes may form in an intriguing multi-step process that involves a concerted motion of many atoms at dislocation defects. We identify such a complex reaction path involving zipper-like motion of such dislocations that initiate structural changes. With low activation barriers <0.3 eV along the optimum path, the conversion process may occur at moderate temperatures. We find all one-dimensional (1D) and 2D chalcogen structures to be semiconducting.
@article{arxiv.1807.07205,
title = {Microscopic Mechanism of the Helix-to-Layer Transformation in Elemental Group VI Solids},
author = {Dan Liu and Xianqing Lin and David Tomanek},
journal= {arXiv preprint arXiv:1807.07205},
year = {2018}
}