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

Abstract 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.