The Li-F-H ternary system at high pressures.

Evolutionary crystal structure prediction searches have been employed to explore the ternary Li-F-H system at 300 GPa. Metastable phases were uncovered within the static lattice approximation, with LiFH, LiFH, LiFH, LiFH, LiFH, and LiFH lying within 50 meV/atom of the 0 K convex hull. All of these phases contain HF (n = 1, 2) anions and Li cations. Other structural motifs such as LiF slabs, H molecules, and F ions are present in some of the low enthalpy Li-F-H structures. The bonding within the HF molecules, which may be bent or linear, symmetric or asymmetric, is analyzed. The five phases closest to the hull are insulators, while LiFH is metallic and predicted to have a vanishingly small superconducting critical temperature. LiFH is predicted to be stable at zero pressure. This study lays the foundation for future investigations of the role of temperature and anharmonicity on the stability and properties of compounds and alloys in the Li-F-H ternary system.