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, CO2 and 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 SiS2 up 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 SiS6 octahedral 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.

Metastable ultracondensed hydrogenous materials

“…Layered SiS 2 structures at high pressures have been found with ab initio calculations that combine evolutionary structure searches and molecular dynamics [24].…”

Strain effects on the structural, electronic, optical and thermoelectric properties of Si2SeS monolayer with puckered honeycomb structure: A first‐principles study

“…Tow‐dimensional dichalcogenides based on silicon was and still received great attention due to their interesting physical properties [35–40]. In this context, SiX 2 (X = S, Se) crystalized under several structures depending on pressure and structure dimensions; I42d space group for three‐dimensional (3D), P3m1 space group for two‐dimensional (2D) multilayered structures and Ibam space group for one‐dimensional (1D) chain‐like structures [35].…”

High-Pressure Structural Evolution of Disordered Polymeric CS$_2$

“…The general high pressure trend of these compounds is to increase the coordination of the cation by the anion in the GPa/tens of GPa pressure range. Indeed, it is well established that the coordination goes from 4 to 6 in SiO 2 [1][2][3], GeO 2 [4,5] and SiS 2 [6][7][8], and from 2 to mixed 3-4 and pure 4 in nonmolecular amorphous and crystalline CO 2 , respectively [9][10][11][12][13][14][15] while, at hundreds of GPa, CO 2 is also predicted to exhibit 6-fold coordination [16]. At variance with the above mentioned systems, CS 2 is a strongly metastable substance, even in the molecular state at ambient conditions.…”