Evolutionary search for superconducting hydrides in the La-Pt-H ternary system under compression

To verify ``hot superconductivity'' recently proposed in lanthanum hydride-based compounds, we explored thermodynamically stable and superconducting phases in the lanthanum (La)-platinum (Pt)-hydrogen (H) ternary system at 20¥,GPa using a computational framework that integrates an evolutionary construction scheme of formation-enthalpy convex hulls, machine learning potential calculations, and density functional theory calculations. Although we found no evidence of the hot superconductivity in this ternary system at the pressure, we predicted a unique compound, LaPtH$_6$. In this compound, PtH$_6$ coordination units are formed, and the hydrogen atoms are arranged in an equilateral triangular pattern that nearly constitutes a two-dimensional kagome lattice between the La and Pt layers, leading to superconductivity at 18.67¥,K. This structure is dynamically stable from ambient pressure to at least 200¥,GPa and the superconducting critical temperature increases from 13.51 to 40.63¥,K.