title: Spectroscopic and ab initio characterization of the [ReH9]2- ion.
abstract: The dynamics and bonding of the hydrido complex Ba[ReH9], containing the D3h face-capped trigonal prismatic [ReH9]2- ion, have been investigated by vibrational spectroscopy and density functional theory (DFT). The combination of infrared, Raman, and inelastic neutron-scattering (INS) spectroscopies has enabled observation of all the modes of the [ReH9]2- ion for the first time. We demonstrate that calculations of the isolated [ReH9]2- ion are unable to reproduce the INS spectrum and that the complete unit cell must be considered with periodic DFT to have reliable results. This is shown to be a consequence of the long-range Coulomb potential present. Analysis of the electronic structure shows that the bonding between the rhenium and the hydrogen is largely covalent. There is a small degree of covalency between the prism hydrides and the barium. The counterion is crucial to the stability of the materials; hence, variation of it potentially offers a method to fine-tune the properties of the material.
authors.affiliation: ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX, U.K. s.f.parker@rl.ac.uk
authors.forename: Stewart F
authors.initials: SF
authors.lastname: Parker
authors.forename: Keith
authors.initials: K
authors.lastname: Refson
authors.forename: Kenneth P J
authors.initials: KP
authors.lastname: Williams
authors.forename: Dale A
authors.initials: DA
authors.lastname: Braden
authors.forename: Bruce S
authors.initials: BS
authors.lastname: Hudson
authors.forename: Klaus
authors.initials: K
authors.lastname: Yvon