Synthesis of technetium hydride TcH$_{1.3}$ at 27 GPa
In this work, we synthesize and investigate lower technetium hydrides at pressures up to 45 GPa using the synchrotron X-ray diffraction, reflectance spectroscopy, and ab initio calculations. In the Tc-H system, the hydrogen content in TcH$_x$ phases increases when the pressure rises, and at 27 GPa we found a new hexagonal (hcp) nonstoichiometric hydride TcH$_{1.3}$. The formation of technetium hydrides is also confirmed by the emergence of a new reflective band at 450-600 nm in the reflectance spectra of TcH$_x$ samples synthesized at 45 GPa. On the basis of the theoretical analysis, we proposed crystal structures for the TcH$_{0.45 \pm 0.05}$ (Tc$_{16}$H$_7$) and TcH$_{0.75 \pm 0.05}$ (Tc$_4$H$_3$) phases previously obtained at 1-2 GPa. The calculations of the electron-phonon interaction show that technetium hydrides TcH$_{1+x}$ do not possess superconducting properties due to the low electron-phonon interaction parameter ($λ\sim 0.23$).