Reactivity of lithium and platinum at elevated densities

Through a series of x-ray diffraction experiments, combined with first-principles calculations, we show that the nobility of platinum can be overcome, reacting with lithium under compression at room temperature. Pressures as low as 2.3 GPa lead to the synthesis of ${\mathrm{Li}}_{11}{\mathrm{Pt}}_{2}$, exhibiting the highest lithium content of any known intermetallic compound. Above 16 GPa, ${\mathrm{Li}}_{11}{\mathrm{Pt}}_{2}$ expels Li and transforms to ${\mathrm{Li}}_{2}\mathrm{Pt}$. This change is accompanied by a transformation in bonding characterized by the formation of one-dimensional Pt-Pt bonds with increasingly covalent character at higher densities.