Pressure-induced metallization of dense (H2S)2H2 with high-Tc superconductivity

Abstract

The high pressure structures, metallization, and superconductivity of recently synthesized H2-containing compounds (H2S)2H2 are elucidated by ab initio calculations. The ordered crystal structure with P1 symmetry is determined, supported by the good agreement between theoretical and experimental X-ray diffraction data, equation of states, and Raman spectra. The Cccm structure is favorable with partial hydrogen bond symmetrization above 37 GPa. Upon further compression, H2 molecules disappear and two intriguing metallic structures with R3m and Im-3m symmetries are reconstructive above 111 and 180 GPa, respectively. The predicted metallization pressure is 111 GPa, which is approximately one-third of the currently suggested metallization pressure of bulk molecular hydrogen. Application of the Allen-Dynes-modified McMillan equation for the Im-3m structure yields high Tc values of 191 K to 204 K at 200 GPa, which is among the highest values reported for H2-rich van der Waals compounds and MH3 type hydride thus far.

Synthesis of lithium polyhydrides above 130 GPa at 300 K

“…(ii) Polyhydrides with nontraditional stoichiometries, in some cases containing an H 2 sublattice, should be stable. (iii) These hydrogen-dense systems may become metallic at much lower pressure than expected for metallic hydrogen and could have a high-temperature superconductivity (8,9). These theoretical results have impelled an active experimental search (e.g., refs.…”

Possible High-Temperature Superconductivity in Hygrogenated Fluorine

“…The ideas of Ashcroft have been recently confirmed by the experiments of Drozdov et al [6] and a series of theoretical papers [7][8][9][10][11][12][13][14] that confirm hydrogen-based hightemperature superconductivity is realized in the sulfur *Corresponding Author: D. A. Papaconstantopoulos: Department of Computational and Data Sciences, George Mason University, Fairfax, Virginia 22030, USA, E-mail: dpapacon@gmu.edu compound H 3 S under 200 GPa pressure. Reference [8] presents a comprehensive set of calculations for H 3 S using the GGM theory.…”

Perspective: Role of structure prediction in materials discovery and design

“…The number of papers published on the theory and modelling of high T c superconductivity in hydrogen sulfide has increased rapidly since 2014, see for example Refs. [15][16][17][18][19][20][21][22][23][24][25][26][27].…”

“…Subsequent to the work of Li et al, 15 Duan et al 16 reported a DFT study of (H 2 S) 2 H 2 at high pressures. They investigated several H/S structures including H 3 S-R3m which is stable at lower pressures and was estimated to have a T c of ∼160 K at 130 GPa, and the higher pressure H 3 S-Im3m phase that was estimated to have a T c of around 200 K at 200 GPa.…”

“…These results are in reasonable agreement with the experimental data of Drozdov et al 3 These data indicated the presence of two superconducting components, with maximum T c 's of about 150 K (R3m) and 200 K (Im3m) at pressures around 150 GPa. DFT studies by Li et al 15 and Duan et al 16 were cited in the experimental papers of Drozdov et al, 2,3 and had clearly influenced their thinking.…”