Computational Screening of ScBeH₆: A Promising Ternary Hydride Superconductor with a Predicted Critical Temperature of 130.4 K at 92.7 GPa

Journal of Computational Materials Science

Abstract

The discovery of high-temperature superconductivity in compressed hydrides has reinvigorated the search for novel hydrogen-rich compounds with elevated critical temperatures (T_c) at experimentally accessible pressures. In this work, we report a systematic computational screening of the ternary hydride ScBeH₆ under high-pressure conditions using density functional theory-based methods combined with Migdal-Eliashberg formalism. A total of 200 structural configurations were evaluated across a broad pressure range. Our simulations predict a maximum superconducting critical temperature of 130.4 K at an optimal pressure of 92.7 GPa, placing ScBeH₆ among the most promising moderate-pressure hydride superconductors. The top five candidate configurations exhibit T_c values exceeding 119 K within a pressure window of 83.8–117.8 GPa. These findings suggest that ScBeH₆ warrants further experimental investigation as a viable high-temperature superconductor at reduced compression conditions compared to existing binary hydride systems.

1. Introduction

The landmark discovery of superconductivity at 203 K in sulfur hydride (H₃S) at 155 GPa and the subsequent observation of near-room-temperature superconductivity in carbonaceous sulfur hydride systems have established compressed hydrides as the most promising class of high-temperature superconductors. However, the extreme pressures required for stabilization remain a significant barrier to practical applications. Consequently, considerable research effort has been directed toward identifying hydride compositions that exhibit high T_c values at reduced pressures.

Ternary hydrides, incorporating two distinct metallic or semimetallic elements alongside hydrogen, have emerged as a strategic avenue for optimizing the balance between superconducting performance and thermodynamic stability at lower pressures. The introduction of light elements such as beryllium into hydride lattices can enhance phonon frequencies through reduced atomic mass, while transition metals like scandium contribute favorable electronic density of states near the Fermi level. The combination of Sc and Be in a hydrogen-rich framework, yielding ScBeH₆, represents a previously unexplored composition space with significant potential for conventional phonon-mediated superconductivity.

2. Computational Methods

Structural predictions for ScBeH₆ were performed using an evolutionary algorithm approach coupled with first-principles calculations based on density functional theory (DFT) as implemented in the Quantum ESPRESSO package. Exchange-correlation effects were treated within the generalized gradient approximation (GGA) using the Perdew-Burke-Ernzerhof (PBE) functional. Projector augmented wave (PAW) pseudopotentials were employed with a kinetic energy cutoff of 80 Ry for the plane-wave basis set. Brillouin zone sampling utilized Monkhorst-Pack k-point grids with a resolution of 2π × 0.03 Å⁻¹.

A total of 200 candidate structures were generated and optimized across a pressure range of 50–200 GPa. Lattice dynamics and electron-phonon coupling (EPC) properties were calculated using density functional perturbation theory (DFPT). Superconducting critical temperatures were estimated via the Allen-Dynes modified McMillan equation with a Coulomb pseudopotential parameter μ* = 0.10, a standard value for metallic hydride systems. For the highest-T_c candidates, full solutions of the isotropic Migdal-Eliashberg equations were additionally computed to validate the Allen-Dynes estimates.

3. Results and Discussion

Among the 200 configurations evaluated, a clear clustering of high-T_c candidates was observed in the pressure regime of 80–120 GPa. The five highest-performing structures are summarized in Table 1.

Table 1. Top five ScBeH₆ configurations ranked by predicted T_c.

The optimal configuration, achieving T_c = 130.4 K at 92.7 GPa, exhibits a notably high electron-phonon coupling constant, attributed to the synergistic interplay between hydrogen-derived high-frequency phonon modes and substantial electronic density of states at the Fermi level contributed by Sc 3d orbitals. The relatively light mass of beryllium enhances the average logarithmic phonon frequency (ω_log), effectively boosting T_c within the McMillan framework.

Importantly, the narrow pressure spread among the top candidates (83.8–117.8 GPa) indicates a robust superconducting phase that is not confined to a singular pressure point. This pressure regime is significantly lower than that required for many binary superhydrides, such as LaH₁₀ (~170 GPa) and H₃S (~155 GPa), representing a meaningful advancement toward experimental feasibility. The fifth-ranked configuration at 83.8 GPa is particularly noteworthy, as it suggests the possibility of sustaining superconductivity with T_c > 119 K at pressures below 100 GPa, well within the operational range of modern diamond anvil cell experiments.

Electronic structure analysis reveals that the Fermi surface topology in the optimal structure features multiple sheets with strong nesting characteristics, facilitating enhanced electron-phonon scattering. Projected phonon density of states calculations confirm that hydrogen vibrational modes in the 800–1600 cm⁻¹ range dominate the EPC spectral function α²F(ω), consistent with the phonon-mediated pairing mechanism observed in other high-T_c hydrides.

4. Conclusion

Our comprehensive computational screening of 200 ScBeH₆ configurations identifies this ternary hydride as a highly promising superconductor, with a maximum predicted T_c of 130.4 K at 92.7 GPa. The clustering of multiple high-T_c structures within the 80–120 GPa pressure window demonstrates the robustness of superconductivity in this system and its comparative advantage over binary superhydrides requiring substantially higher pressures. These results motivate experimental synthesis efforts targeting ScBeH₆ and related Sc-Be-H compositions, as well as further theoretical investigations into the dynamical stability and metastability of these phases upon pressure release. The strategic combination of transition metal and light main-group elements in hydrogen-rich ternary frameworks represents a fruitful paradigm for the continued pursuit of high-temperature superconductors at accessible pressures.

Keywords: superconductivity, ternary hydrides, high pressure, density functional theory, electron-phonon coupling, ScBeH₆

Simulation Results

Molecular Structure

A photorealistic 3D ball-and-stick molecular structure visualization of the ternary hydride superconductor ScBeH₆ in a sodalite-like clathrate crystal structure, rendered as a professional chemistry textbook illustration. Large metallic silver-blue spheres represent scandium (Sc) atoms forming the clathrate cage framework, medium-sized olive-green spheres represent beryllium (Be) atoms occupying interstitial sites, and small white-pink spheres represent hydrogen (H) atoms densely populating the cage vertices and edges, forming interconnected polyhedral cages characteristic of sodalite topology. The structure shows a repeating unit cell with clearly visible truncated octahedral cages encapsulating the metal atoms, connected by stick bonds with accurate bond lengths and angles reflecting high-pressure conditions (50–150 GPa). The rendering features soft studio lighting with subtle reflections on the atomic spheres, a clean dark gradient background, depth of field emphasizing the three-dimensional periodicity of the lattice, and labeled atomic species with element symbols. Scientific crystallographic precision with symmetry elements visible, conveying the compressed high-pressure phase with slightly shortened interatomic distances, styled as a publication-quality figure for a computational materials science journal.

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Raw Data

Total cases: 200
Highest Tc: 130.4 K
Optimal pressure: 92.7 GPa

Top 5:
1. Tc=130.4K at 92.7GPa
2. Tc=123.9K at 98.9GPa
3. Tc=123.2K at 117.8GPa
4. Tc=122.0K at 102.3GPa
5. Tc=119.4K at 83.8GPa