title: Crystal structures and superconductivity of technetium hydrides under pressure.
abstract: Guided by a simple strategy in search of new superconducting materials, we have performed extensive simulations on crystal structures and electronic properties of Tc-H compounds at high pressures. Three stoichiometries, namely TcH, TcH2, and TcH3, were predicted to be stable under high pressure. The chemical bonding characters of Tc-H compounds were investigated by introducing the electron localization function and electronic projected density of states, which show that the stable Tc-H compounds including TcH, TcH2and TcH3are all classified as ionic crystals as a result of Tc → H charge transfer. Based on the Bardeen-Cooper-Schrieffer theory and estimated from the Allen-Dynes modified McMillan equation, the superconducting critical temperature (Tc) values of the I4/mmm phase for TcH2are 5 K at 100 GPa and 11 K at 200 GPa. Moreover, it is found that Cmcm-TcH2and P42/mmc-TcH3at 300 GPa have Tcvalues of 9 K and 10 K, respectively. Our current results significantly enrich the crystal structures of the Tc-H system and provide a further understanding of their structural features and physical properties.
authors.affiliation: College of Physics and Electronic Information, Luoyang Normal College, Henan Luoyang, 471022, P. R. China.
authors.forename: Xiaofeng
authors.initials: X
authors.lastname: Li
authors.affiliation: Geophysical Laboratory, Carnegie Institution of Washington, Washington, DC 20015, USA.
authors.forename: Hanyu
authors.initials: H
authors.lastname: Liu
authors.affiliation: Beijing Computational Science Research Center, Beijing 100084, P. R. China. fpeng@calypso.cn.
authors.forename: Feng
authors.initials: F
authors.lastname: Peng