Structure and electronic properties of BaH2 at high pressure

The structure of BaH2 at high pressure up to 58 GPa has been investigated with synchrotron powder x-ray diffraction. A structural phase transition from the low pressure Ni-2 In structure to a simple hexagonal structure, which started at 40 GPa and was completed at approximately 45 GPa, was confirmed. A loss of Raman signal in this pressure range suggests that an insulator to metal transition has occurred. This observation is corroborated with first-principles calculations. The investigation of the electron-phonon coupling shows that the metallic phase is a very weak superconductor with an estimated superconducting critical temperature T-c in the range of mK. (C) 2009 Elsevier Ltd. All rights reserved.