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Issue 21, 2013
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Molecular dynamics investigation of the disordered crystal structure of hexagonal LiBH4

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Abstract

The crystal structure of the hexagonal phase of solid lithium borohydride (LiBH4) is studied by ab initio molecular dynamics simulations of both the low and high-temperature phases. A temperature range of 200–535 K is simulated with the aim of characterising the disorder in the high-temperature structure in detail. The mechanism and kinetics of the reorientational motion of the borohydride units (BH4) are determined and are consistent with published neutron scattering experiments; it is found that rotational diffusivity increases by an order of magnitude at the phase transition temperature. The average equilibrium orientation is characterised by a broad distribution of orientations, and reorientational jumps do not occur between sharply defined orientations. In addition, split positions with partial occupancy for the lithium and boron atoms are found (in agreement with previous theoretical studies), which, together with the disordered BH4 orientational distribution in equilibrium, lead to the conclusion that the correct crystallographic space group of the high-temperature phase is P63/mmc rather than P63mc.

Graphical abstract: Molecular dynamics investigation of the disordered crystal structure of hexagonal LiBH4

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Publication details

The article was received on 14 Dec 2012, accepted on 29 Jan 2013 and first published on 29 Jan 2013


Article type: Paper
DOI: 10.1039/C3CP44520H
Citation: Phys. Chem. Chem. Phys., 2013,15, 8081-8087
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    Molecular dynamics investigation of the disordered crystal structure of hexagonal LiBH4

    P. C. Aeberhard, K. Refson and W. I. F. David, Phys. Chem. Chem. Phys., 2013, 15, 8081
    DOI: 10.1039/C3CP44520H

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