More Like this

1. High-temperature superconductivity in quinary clathrate hydrides under pressure

   https://doi.org/10.1103/4hr1-vcvk  

   Zhang, Peiyu; Guan, Hongyi; Li, Hefei; Zhong, Xin; Hemley, Russell J; Liu, Hanyu (August 2025, Physical Review B)

   The search for high-temperature superconductivity among pressure-stabilized hydrides has received great interest since theory-directed clathrate hydrides, such as CaH6, YH6, YH9, and LaH10, were synthesized and shown to exhibit a superconducting critical temperature (Tc) above 200 K. However, further tuning the superconductivity and stability of these prominent hydrides to enhance their applicability remains a significant challenge. Here, we take the sodalite-like clathrate prototype MH6 (M = Ca, Y, etc.) as an example to investigate the stability and superconductivity of multicomponent metal hydrides containing four different metal atoms for each structure. High-throughput simulations of 1820 ABCDH24 quinary hydrides with initial symmetry of F4" 3m, where A, B, C, and D represent different metal atoms were performed. The calculations reveal 119 structures that are dynamically stable at 300 GPa and 67 structures exhibit superconductivity exceeding 200 K, and 20 are found to have Tcs above 260 K. Notable among these quinary alloy hydrides, (Na,Zr,Mg,Hf)H6 is predicted to have a Tc approaching room temperature at 250 GPa. Both configurational and vibrational entropy play important roles in stabilizing these alloy structures. (Na,Y,Zr,Hf)H6, (Mg,Zr,Sc,Y)H6, and (Mg,Hf,Ca,Zr)H6 were computed to be thermodynamically stable, making them promising candidates for experimental synthesis. These quinary superconducting hydrides may facilitate realization of very high-temperature superconductors that are stable over a broader range of conditions than those found for binary or ternary systems. 

   more » « less
2. Unlocking the Origin of High‐Temperature Superconductivity in Molecular Hydrides at Moderate Pressures

   https://doi.org/10.1002/adfm.202415910  

   Zhao, Wendi; Ellis, Austin; Duan, Defang; Wang, Hongwei; Jiang, Qiwen; Du, Mingyang; Cui, Tian; Miao, Maosheng (November 2024, Advanced Functional Materials)

   Abstract The current pressing challenge in the field of superconducting hydride research is to lower the stable pressure of such materials for practical applications. Molecular hydrides are usually stable under moderate pressure, but the underlying metallization mechanism remains elusive. Here, the important role of chemical interactions in governing the structures and properties of molecular hydrides is demonstrated. A new mechanism is proposed for obtaining high‐temperature and even room‐temperature superconductivity in molecular hydrides and report that the ternary hydride NaKH₁₂hostsT_cvalues up to 245 K at moderate pressure of 60 GPa. Both the excellent stability and superconductivity of NaKH₁₂originate from the fact that the localized electrons in the interstitial region of the metal lattice occupying the crystal orbitals well matched with the hydrogen lattice and forming chemical templates to assist the assembly of H₂units. These localized electrons weaken the H─H covalent bonds and improve the charge connectivity between the H₂units, ensuring the strong coupling between electrons and hydrogen‐dominated optical phonons. The theory provides a key perspective for understanding the superconductivity of molecular hydrides with various structural motifs, opening the door to obtaining high‐temperature superconductors from molecular hydrides at moderate pressures. 

   more » « less
3. Hot Hydride Superconductivity Above 550 K

   https://doi.org/10.3389/femat.2022.837651  

   Grockowiak, A. D.; Ahart, M.; Helm, T.; Coniglio, W. A.; Kumar, R.; Glazyrin, K.; Garbarino, G.; Meng, Y.; Oliff, M.; Williams, V.; et al (March 2022, Frontiers in Electronic Materials)

   The search for room temperature superconductivity has accelerated in the last few years driven by experimentally accessible theoretical predictions that indicated alloying dense hydrogen with other elements could produce conventional superconductivity at high temperatures and pressures. These predictions helped inform the synthesis of simple binary hydrides that culminated in the discovery of the superhydride LaH 10 with a superconducting transition temperature T c of 260 K at 180 GPa. We have now successfully synthesized a metallic La-based superhydride with an initial T c of 294 K. When subjected to subsequent thermal excursions that promoted a chemical reaction to a higher order system, the T c onset was driven irreversibly to 556 K. X-ray characterization confirmed the formation of a distorted LaH 10 based backbone that suggests the formation of ternary or quaternary compounds with substitution at the La and/or H sites. The results provide evidence for hot superconductivity, aligning with recent predictions for higher order hydrides under pressure. 

   more » « less
4. Designing multicomponent hydrides with potential high T _c superconductivity

   https://doi.org/10.1073/pnas.2413096121  

   Denchfield, Adam; Park, Hyowon; Hemley, Russell J (November 2024, Proceedings of the National Academy of Sciences)

   While hydrogen-rich materials have been demonstrated to exhibit high T_csuperconductivity at high pressures, there is an ongoing search for ternary, quaternary, and more chemically complex hydrides that achieve such high critical temperatures at much lower pressures. First-principles searches are impeded by the computational complexity of solving the Eliashberg equations for large, complex crystal structures. Here, we adopt a simplified approach using electronic indicators previously established to be correlated with superconductivity in hydrides. This is used to study complex hydride structures, which are predicted to exhibit promisingly high critical temperatures for superconductivity. In particular, we propose three classes of hydrides inspired by the Fm $\overline{3}$m RH ${}_3$structures that exhibit strong hydrogen network connectivity, as defined through the electron localization function. The first class [RH ${}_{11}$X ${}_3$Y] is based on a Pm $\overline{3}$m structure showing moderately high T_c, where the T_cestimate from electronic properties is compared with direct Eliashberg calculations and found to be surprisingly accurate. The second class of structures [(RH ${}_{11}$) ${}_2$X ${}_6$YZ] improves on this with promisingly high density of states with dominant hydrogen character at the Fermi energy, typically enhancing T_c. The third class [(R ${}^1$H ${}_{11}$)(R ${}^2$H ${}_{11}$)X ${}_6$YZ] improves the strong hydrogen network connectivity by introducing anisotropy in the hydrogen network through a specific doping pattern. These design principles and associated model structures provide flexibility to optimize both T_cand the structural stability of complex hydrides. 

   more » « less
5. Design of high-temperature superconductors at moderate pressures by alloying AlH3 or GaH3

   https://doi.org/10.1063/5.0159590  

   Liang, Xiaowei; Wei, Xudong; Zurek, Eva; Bergara, Aitor; Li, Peifang; Gao, Guoying; Tian, Yongjun (January 2024, Matter and Radiation at Extremes)

   Since the discovery of hydride superconductors, a significant challenge has been to reduce the pressure required for their stabilization. In this context, we propose that alloying could be an effective strategy to achieve this. We focus on a series of alloyed hydrides with the AMH6 composition, which can be made via alloying A15 AH3 (A = Al or Ga) with M (M = a group ⅢB or IVB metal), and study their behavior under pressure. Seven of them are predicted to maintain the A15-type structure, similar to AH3 under pressure, providing a platform for studying the effects of alloying on the stability and superconductivity of AH3. Among these, the A15-type phases of AlZrH6 and AlHfH6 are found to be thermodynamically stable in the pressure ranges of 40–150 and 30–181 GPa, respectively. Furthermore, they remain dynamically stable at even lower pressures, as low as 13 GPa for AlZrH6 and 6 GPa for AlHfH6. These pressures are significantly lower than that required for stabilizing A15 AlH3. Additionally, the introduction of Zr or Hf increases the electronic density of states at the Fermi level compared with AlH3. This enhancement leads to higher critical temperatures (Tc) of 75 and 76 K for AlZrH6 and AlHfH6 at 20 and 10 GPa, respectively. In the case of GaMH6 alloys, where M represents Sc, Ti, Zr, or Hf, these metals reinforce the stability of the A15-type structure and reduce the lowest thermodynamically stable pressure for GaH3 from 160 GPa to 116, 95, 80, and 85 GPa, respectively. Particularly noteworthy are the A15-type GaMH6 alloys, which remain dynamically stable at low pressures of 97, 28, 5, and 6 GPa, simultaneously exhibiting high Tc of 88, 39, 70, and 49 K at 100, 35, 10, and 10 GPa, respectively. Overall, these findings enrich the family of A15-type superconductors and provide insights for the future exploration of high-temperature hydride superconductors that can be stabilized at lower pressures. 

   more » « less