Structural and Superconducting Parameters of Highly Compressed H3S

The discovery of superconductivity in pressurized H3S [1] initiated a wide range of experimental and theoretical studies of compressed hydrides in which room-temperature superconductivity is in demand. Recently, a new milestone progress has been reported in the field, namely, direct measurements of the superconducting gap amplitude Δ ( T ) in highly compressed sulfur [46], H3S and D3S [47]. This study examines recent experimental XRD data reported on H3S [47] and found that H3S (at pressure 151\; < P < 158~\,GPa ) exhibits nanosized grains with average size D = 24 ± 2 nm and remarkably low microstrain ε = 0.07 ± 0.04%. Further analysis of reported experimental data shows that the H3S has the Debye temperature Θ _D = 1294 ± 24\,~K , the electron–phonon coupling constant γ _e - ph = 2.30 , specific heat jump at the superconducting transition temperature Δ C_elγ T_c = 1.5 ± 0.6 , and gap-to-transition temperature ratio 2Δ ( 0 )k_BT_c = 3.7 ± 0.3 . The derived values are in a good agreement with the values calculated by first-principles calculations.