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 $$\Delta \left( T \right)$$ 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 $$151{\;} < P < 158~\,{\text{GPa}}$$ ) 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 $${{{{\Theta }}}_{{\text{D}}}} = 1294 \pm 24\,~{\text{K}}$$ , the electron–phonon coupling constant $${{\gamma }_{{{\text{e}} - {\text{ph}}}}} = 2.30$$ , specific heat jump at the superconducting transition temperature $$\frac{{\Delta {{C}_{{{\text{el}}}}}}}{{\gamma {{T}_{{\text{c}}}}}} = 1.5 \pm 0.6$$ , and gap-to-transition temperature ratio $$\frac{{2\Delta \left( 0 \right)}}{{{{k}_{{\text{B}}}}{{T}_{{\text{c}}}}}} = 3.7 \pm 0.3$$ . The derived values are in a good agreement with the values calculated by first-principles calculations.