title: Creating new layered structures at high pressures: SiS2.
abstract: Old and novel layered structures are attracting increasing attention for their physical, electronic, and frictional properties. SiS2, isoelectronic to SiO2, CO2and CS2, is a material whose phases known experimentally up to 6 GPa exhibit 1D chain-like, 2D layered and 3D tetrahedral structures. We present highly predictive ab initio calculations combined with evolutionary structure search and molecular dynamics simulations of the structural and electronic evolution of SiS2up to 100 GPa. A highly stable CdI2-type layered structure, which is octahedrally coordinated with space group surprisingly appears between 4 and up to at least 100 GPa. The tetrahedral-octahedral switch is naturally expected upon compression, unlike the layered character realized here by edge-sharing SiS6octahedral units connecting within but not among sheets. The predicted phase is semiconducting with an indirect band gap of about 2 eV at 10 GPa, decreasing under pressure until metallization around 40 GPa. The robustness of the layered phase suggests possible recovery at ambient pressure, where calculated phonon spectra indicate dynamical stability. Even a single monolayer is found to be dynamically stable in isolation, suggesting that it could possibly be sheared or exfoliated from bulk -SiS2.
authors.affiliation: Department of Experimental Physics, Comenius University, Mlynská Dolina F2, 842 48 Bratislava, Slovakia.
authors.forename: Dušan
authors.initials: D
authors.lastname: Plašienka
authors.affiliation: Department of Experimental Physics, Comenius University, Mlynská Dolina F2, 842 48 Bratislava, Slovakia.
authors.forename: Roman
authors.initials: R
authors.lastname: Martoňák
authors.affiliation: International School for Advanced Studies (SISSA) and CNR-IOM Democritos, Via Bonomea 265, 34136 Trieste, Italy.|The Abdus Salam International Centre for Theoretical Physics (ICTP), Strada Costiera 11, 34151 Trieste, Italy.
authors.forename: Erio
authors.initials: E
authors.lastname: Tosatti