(La,Th)H₁₀: Potential High-T_c (242 K) Superconductors Stabilized Thermodynamically below 200 GPa

Abstract

The recent experimental discovery of high-pressure superconductivity in (La,Y)H 10 , (La,Ce)H 9 , (La,Ce)H 10 , (Y,Ce)H 9 , and (La,Nd)H 10 confirms that ternary rare-earth clathrate hydrides are promising candidates for high-temperature superconductors. This study theoretically demonstrates the ability of actinide-metal thorium (Th), rare-earth-metal lanthanum (La), and hydrogen to form stable ternary hydrides under 200 GPa. Using the evolutionary algorithm combined with the first-principles calculations and strong-coupling Eliashberg approach, we predicted the pressuredependent ternary phase diagram of La x Th y H z , particularly, the case of (La 1−x Th x )H n [or designated as (La,Th)H n for simplicity]. Our calculations revealed that hydrogen-rich phases such as (La,Th)H 10 are thermodynamically stable below 200 GPa, with phase decomposition occurring in (La,Th)H 9 above 150 GPa. Moreover, the electron−phonon coupling (EPC) calculations show that the (La,Th)H 10 series could function as potential superconductors, of which I4/mmm-La 3 ThH 40 (at 200 GPa) exhibited a large EPC constant of λ = 2.46 with the highest transition temperature (T c ) of 242 K.

High-temperature superconductivities and crucial factors influencing the stability of LaThH12 under moderate pressures

“…Here, we successfully reproduced the previously predicted structures such as Pm 3-LaThH 6 , P 1̄-La 3 ThH 16 , P 2/ m -LaTh 3 H 16 , Cmmm -LaThH 8 , C 2/ m -La 2 ThH 12 , C 2/ m -LaTh 2 H 12 , I 4/ mmm -LaTh 3 H 40 and R 3̄ m -LaThH 20 , confirming the reliability of our work, and their corresponding T c 's are summarized in Table S1 (ESI†). 46 Notably, in contracted to LaYH 12 synthesized under high-pressures above 1 Mbar, we observed that the LaThH 12 falls within 30 meV per atom above the convex hull line in the range of 30–300 GPa. Based on previous statistical analysis indicating that around ninety percent of compounds in the Inorganic Crystal Structure Database possess instability energy Δ H > 67 ± 2 meV per atom, indicating that LaThH 12 shows potential for synthesis.…”

Stabilizing Phonon-Mediated High-Temperature Superconductivity via Helium Substitution in Pressurized Lithium Hexahydride

“…Regarding the detail of λ in Table , the theoretical explanation of how the integrated λ is described is thoroughly covered in refs and and is widely applied to materials such as lanthanum hydrides, actinium beryllium hydrides, and thorium lanthanum hydrides . These studies show that the λ constants are quite similar.…”

Theoretical Insights into High-Tc Superconductivity of Structurally Ordered YThH18: A First-Principles Study

“…In experiments, the use of Y–Th alloy as a precursor for the synthesis of Y–Th–H hydrides under high-temperature and high-pressure conditions can facilitate the formation of disordered alloyed ternary hydrides by readily overcoming the energy barrier posed by the enthalpy of formation. 45 A recent investigation into the La–Th–H-based ternary hydrides by Song et al 46 demonstrated the possibility of disordered alloy structure formation. This study also suggests that the ordered compositions at ambient conditions gradually stabilize into disordered phases with increasing temperature due to an increase in the configurational entropy of mixing.…”

“…It is widely recognized that elements sharing similar properties such as atomic radii, electronegativity, and electronic configuration typically exhibit a higher propensity for disordered substitutional alloy formation due to its higher configurational entropy. 40 − 43 In this vein, recent works 43 − 46 suggest that multiple predicted ternary phases could have more stable, disordered counterparts. This seems to hold even for our Y–Th–H systems because Y and Th atoms have similar physical characteristics (electronegativities of 1.3 and 1.22 on the Pauling scale, respectively, and identical atomic radii of 1.80 Å).…”