### Session S39: Focus Session: Hydrogen Storage IV

2:30 PM–5:30 PM, Wednesday, March 7, 2007

Chair: Robert Bowman, Jet Propulsion Laboratory

Abstract ID: BAPS.2007.MAR.S39.7

### Abstract: S39.00007 : Cohesion of BaReH$_9$ and BaMnH$_9$: Density Functional Calculations and Prediction of (MnH$_9$)$^{2-}$ Salts

4:06 PM–4:18 PM

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#### Authors:

David Singh
(Oak Ridge National Laboratory)

M. Gupta
(Universite Paris-Sud)

R. Gupta
(CEA, Saclay)

Density functional calculations are used to calculate the structural and electronic properties of BaReH$_9$ and to analyze the bonding in this compound. This compound has an exceptionally high H to metal ratio of 4.5. The high coordination of Re in BaReH$_9$ is due to bonding between Re 5d states and states of d-like symmetry formed from combinations of H s orbitals in the H$_9$ cage. This explains the structure of the material, its short bond lengths and other physical properties, such as the high band gap. We compare with results for hypothetical BaMnH$_9$, which we find to have similar bonding and cohesion to the Re compound. This suggests that it may be possible to synthesize (MnH$_9$)$^{2-}$ salts. Depending on the particular cation, such salts may have exceptionally high hydrogen contents, in excess of 10 weight \%.

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2007.MAR.S39.7