Superconducting high-pressure phases of disilane

Abstract

High-pressure structures of disilane (Si 2 H 6 ) are investigated extensively by means of first-principles density functional theory and a random structure-searching method. Three metallic structures with P-1, Pm-3m, and C2∕c symmetries are found, which are more stable than those of XY 3 -type candidates under high pressure. Enthalpy calculations suggest a remarkably wide decomposition (Si and H 2 ) pressure range below 135 GPa, above which three metallic structures are stable. Perturbative linear-response calculations for Pm-3m disilane at 275 GPa show a large electron-phonon coupling parameter λ of 1.397 and the resulting superconducting critical temperature beyond the order of 10 2 K. metallization | new phase | solid disilane I t is known that the highest superconductive critical temperature (T c ) found for a conventional superconductor is 39 K for MgB 2 (1) at ambient pressure. Cuprate superconductors have much higher critical temperatures. The cuprate superconductor discovered has a critical temperature of 93 K (2), and mercury-based cuprates have critical temperatures in excess of 130 K. Pressure causes extraordinary changes in materials and modifies their properties. This often provides a path for synthesis of novel materials. Applying BCS theory to hypothetic metallic hydrogen, Ashcroft realized that it is a conventional superconductor with a very high-T c (3). A T c of the order of 10 2 K was further proposed under very strong compression by quantitative calculations (4). This value compares favorably with those in cuprate superconductors. However, hydrogen remains insulating up to extremely high pressures, at least up to about 342 GPa (5).It was recently predicted that group IVa hydrides would also present a high superconducting critical temperature, while becoming metallic at lower pressures due to chemical precompression (6). Theoretical (7-12) and experimental (13-15) studies of silane, and theoretical studies of germane (16) and stannane (17, 18), have investigated possible metallization and superconducting phase transitions at high pressures. Indeed, the theoretical studies on germane and stannane have predicted very high T c of 64 K at 220 GPa (16) and 80 K at 120 GPa (17), respectively. These results sufficiently encouraged us to prompt studies on a wider range of hydrides to confirm the prediction (6). Disilane containing a large fraction (3∕4) of H atoms is also an important hydrogen-rich compound and leads to interesting properties under high pressure. Furthermore, it is more readily available for experimental studies because of the higher boiling and melting points than silane, germane, and stannane. However, studies on disilane are very scarce.Here, we have explored the crystal structures of disilane in a wide pressure range from 50 to 400 GPa, and three favored structures, i.e., P-1, Pm-3m, and C2∕c, are found above 135 GPa. Remarkably, the large T c of 80 K at 200 GPa for P-1 and 139 K at 275 GPa for Pm-3m are predicted by quantitative calculations. Up to now, the superconductive T c of...

Theoretical study of the ground-state structures and properties of niobium hydrides under pressure

“…However, there are many known AH 3 -type compounds, for example, YH 3 55 and the predicted low-and high-pressure structures Cmcm, P 6 3 /mmc, and C2/m YH 3 , 54 and P m-3m for Si 2 H 6 . 56 Among these structures, the F m-3m and P 6 3 /mmc structures can actually be obtained by placing H atoms in all the T and O sites of an fcc and hcp niobium lattices, respectively [see Figs. 7(a) and 7(b)].…”

The characterization of high-pressure superconducting state in compound: The strong-coupling description

“…On the basis of the results presented in Fig. 3, it is easy to notice that the critical temperature is very high in the whole range of the considered The obtained result is related to the fact that T C in [31] has been estimated on the basis of the classical Allen-Dynes formula, which significantly lowers its value. Generalizing the achieved result, Fig.…”

“…For Si 2 H 6 , the Eliashberg function has been calculated in [31]; the maximum phonon frequency (Ω max ) is equal to 284.41 meV.…”

Perspective: Role of structure prediction in materials discovery and design

“…57 However, our structure searches suggest this phase to be unstable to decomposition at high pressures. High-temperature superconductivity was also predicted in a number of metallic hydrides [57][58][59][60][61][62][63][64][65][66][67] but most of the predicted T c 's were not realized. FIG.…”