Lanthanum decahydride is a polyhydride or superhydride compound of lanthanum and hydrogen (LaH₁₀) that has shown evidence of being a high-temperature superconductor. It was the first metal superhydride to be theoretically predicted,^[2][3] synthesized,^[4] and experimentally confirmed^[5] to superconduct at near room-temperatures. It has a superconducting transition temperature T_C around 250 K (−23 °C; −10 °F) at a pressure of 150 gigapascals (22×10^⁶ psi), and its synthesis required pressures above approximately 160 gigapascals (23×10^⁶ psi).^[6][7]

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Since its discovery,^[8] the superconducting properties of LaH₁₀ and other lanthanum-based superhydrides have been experimentally confirmed in multiple independent experiments.^{[9][10][11][12]} The compound exhibits a Meissner effect below the superconducting transition temperature.^[13] A cubic form can be synthesized at 1,000 K (730 °C; 1,340 °F),^[6] and a hexagonal crystal structure can be formed at room temperature.^[14] Further reports indicate T_c is increased with nitrogen doping,^[15] and decreased with the introduction of magnetic impurities.^[16]

The cubic form has each lanthanum atom surrounded by 32 hydrogen atoms, which form the vertices of an 18-faced shape called a chamfered cube.^[17]

A similar compound, lanthanum boron octahydride, was computationally predicted to be a superconductor at 126 K (−147 °C; −233 °F) and pressure 50 gigapascals (7.3×10^⁶ psi).^[18]

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