Pressure-temperature phase diagram of LiBH4:: Synchrotron x-ray diffraction experiments and theoretical analysis

An in situ combined high-temperature high-pressure synchrotron radiation diffraction study has been carried out on LiBH(4). The phase diagram of LiBH(4) is mapped to 10 GPa and 500 K, and four phases are identified. The corresponding structural distortions are analyzed in terms of symmetry-breaking atomic position shifts and anion ordering. Group-theoretical and crystal-chemical considerations reveal a nontrivial layered structure of LiBH(4). The layers and their deformations define the structural stability of the observed phases.