Researchers are actively pursuing ambient-pressure superconducting hydrides to overcome the limitations of materials requiring extreme compression for functionality. Qun Wei, Xinyu Wang and Jing Luo, all from Xidian University, alongside Meiguang Zhang from Baoji University of Arts and Sciences and Bing Wei from Xidian University et al., report the design and computational evaluation of LiMgZr2H12, a novel hydride structure predicted to exhibit superconductivity at 60.8 K and standard pressure. Their first-principles calculations reveal that lithium doping substantially enhances the superconducting properties compared to MgZrH6, increasing both the electron density of states near the Fermi level and the superconducting figure of merit to 1.56. This work represents a significant step towards realising practical, high-temperature superconductivity without the need for high-pressure environments and offers a pathway for the rational design of future ambient-pressure hydrides.
Ambient pressure superconductivity in a quaternary hydride LiMgZr2H12 is reported
Scientists have designed a novel quaternary hydride, LiMgZr2H12, exhibiting superconductivity at 60.8 K under ambient pressure. This achievement circumvents a major limitation of previously discovered hydrogen-rich superconductors, which typically require extreme compression to achieve superconducting states.
The research details the creation and thorough analysis of this new material, demonstrating its potential to unlock practical applications currently hindered by high-pressure requirements. Through first-principles calculations, researchers established the thermodynamic, mechanical, and dynamical stability of the LiMgZr2H12 structure, confirming its viability as a room-temperature superconductor candidate.
The study builds upon investigations of the MgZrH2n family, constructing the LiMgZr2H12 structure with Pmmm symmetry and rigorously evaluating its properties. Electron-phonon coupling analysis revealed the critical temperature of 60.8 K, a significant finding for ambient-pressure superconductivity. Lithium doping proved crucial, substantially increasing the contribution of hydrogen atoms to the electron density of states near the Fermi level and enhancing the electron-phonon coupling constant.
This enhancement directly translates to improved superconducting characteristics compared to the parent compound, MgZrH6. LiMgZr2H12 demonstrates a superconducting figure of merit of 1.56, markedly exceeding the 1.51 value observed in MgZrH6. This superior figure of merit underscores the material’s outstanding potential for technological applications, including energy transmission and high-field magnets. The work provides a pathway for the rational design of ambient-pressure, high-temperature superconductors.
Computational methodology for LiMgZr2H12 structural and electronic property determination is presented
First-principles calculations underpinned the investigation of the LiMgZr2H12 structure and its potential for ambient-pressure superconductivity. The research commenced with the construction of the LiMgZr2H12 crystal structure, possessing Pmmm symmetry, inspired by earlier studies of the MgZrH2n family of hydrogen-rich compounds.
Total-energy calculations were then performed using the QUANTUM ESPRESSO package, employing plane-wave basis sets and the Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation. Projector augmented-wave (PAW) potentials were utilised to describe the interaction between the core and valence electrons, ensuring accurate representation of the electronic structure.
A 16x16x16 k-point mesh, generated using the Monkhorst-Pack scheme, was employed for Brillouin-zone integrations to achieve convergence in the calculations of electronic properties. The convergence criteria for energy and force were set to 10−5 eV and 0.01 eV/Å, respectively, guaranteeing the reliability of the results.
Dynamical stability was assessed through phonon calculations performed with the small-mass supercell method, identifying any imaginary frequencies that would indicate structural instability. Electron-phonon coupling (EPC) analysis was conducted to determine the superconducting critical temperature (Tc), revealing a value of 60.8 K for LiMgZr2H12 at ambient pressure.
This analysis involved calculating the EPC constant, which quantifies the strength of the electron-phonon interaction, and assessing the contribution of hydrogen atoms to the density of states near the Fermi level. The superconducting figure of merit, calculated as 1.56, demonstrates a significant improvement over MgZrH6, highlighting the enhanced potential of LiMgZr2H12 for practical superconducting applications. Crystal Orbital Hamilton Population (COHP) analysis, utilising the LOBSTER program, further elucidated the chemical bonding characteristics within the structure.
Thermodynamic, mechanical and dynamic stability underpin superconductivity in LiMgZr2H12 compounds
Calculations reveal a superconducting critical temperature (Tc) of 60.8 K for LiMgZr2H12 at ambient pressure. This quaternary hydride demonstrates substantial promise for practical applications due to its unique properties and stability. The research focused on evaluating the thermodynamic, mechanical, and dynamical stability of this hydrogen-rich compound using first-principles calculations.
Formation energy calculations confirm that the LiMgZr2H12 structure is thermodynamically stable, while elastic constants satisfy the Born stability criterion, indicating mechanical stability. Phonon dispersion analysis further demonstrates dynamic stability at ambient conditions, with all phonon modes in the Brillouin zone exhibiting positive frequencies.
The structure features H12 cages centered by Zr, Li, and Mg atoms, with a minimum H, H distance of 1.76 Å, significantly longer than the standard covalent bond length of 0.74 Å. Electron-phonon coupling (EPC) analysis yielded an EPC constant λ of 2.22 for LiMgZr2H12, exceeding that of MgB2 at ambient pressure (λ = 0.61) and MgZrH6 at 36 GPa (λ = 1.13).
The contribution of hydrogen atoms to the electron density of states near the Fermi level is significantly increased by Li doping. Low-frequency phonon modes primarily originate from vibrations of Li, Zr, and Mg atoms, contributing 48% to the total EPC constant, while H-atom vibrations dominate intermediate- and high-frequency modes, accounting for 52%.
The superconducting figure of merit for LiMgZr2H12 was calculated to be 1.56, a 34% improvement over MgZrH6. This value also surpasses those of H3S (1.27), YH9 (1.19), and LaH10 (1.43), indicating exceptional potential for practical superconducting applications. Analysis of the electron localization function (ELF) reveals ionic bonding between metal and hydrogen atoms, with minimal electron localization between hydrogen atoms, confirming the stabilization of hydrogen as monatomic species.
Researchers have identified a lithium-magnesium-zirconium hydride, LiMgZr2H12, exhibiting a superconducting critical temperature of 60.8 Kelvin at ambient pressure. This compound demonstrates enhanced superconducting properties compared to magnesium-zirconium hydride, achieved through lithium doping which increases the hydrogen contribution to the electronic density of states near the Fermi level and strengthens electron-phonon coupling.
The calculated superconducting figure of merit for LiMgZr2H12 is 1.56, exceeding that of MgZrH6 by approximately 34 percent, suggesting considerable promise for technological applications. The stability of LiMgZr2H12 is attributed to strong zirconium-hydrogen interactions, and the electronic structure reveals minimal hydrogen-hydrogen bonding.
While the material is predicted to be metastable, requiring specific synthesis conditions such as rapid quenching or inert gas handling, its performance surpasses existing hydrides at comparable conditions. This work offers theoretical guidance for the design of ambient-pressure hydrogen storage materials.
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🗞 Design of a 60.8 K superconducting hydride LiMgZr2H12 at ambient pressure via Lithium doping
🧠ArXiv: https://arxiv.org/abs/2602.03471