title: Structures of Si and Ge nanowires in the subnanometer range.
abstract: We report an ab initio investigation of several structures of pristine Si and Ge nanowires with diameters between 0.5 and 2.0 nm. We consider nanowires based on the diamond structure, high-density bulk structures, and fullerenelike structures. Our calculations indicate a transition from sp3 geometries to structures with higher coordination, for diameters below 1.4 nm. We find that diamond-structure nanowires are unstable for diameters smaller than 1 nm, undergoing considerable structural transformations towards amorphouslike wires. For diameters between 0.8 and 1 nm, filled-fullerene wires are the most stable. For even smaller diameters (approximately 0.5 nm), we find that a simple hexagonal structure is particularly stable for both Si and Ge.
authors.affiliation: Departamento de Física, ICEX, Universidade Federal de Minas Gerais, CP 702, 31270-901 Belo Horizonte, Minas Gerais, Brazil.
authors.forename: R
authors.initials: R
authors.lastname: Kagimura
authors.forename: R W
authors.initials: RW
authors.lastname: Nunes
authors.forename: H
authors.initials: H
authors.lastname: Chacham