First-principles study on the high-$T_\text{c}$ superconductivity of Mg-Ti-H ternary hydrides up to the liquid-nitrogen temperature range under high pressures
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2026
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| _version_ | 1866910015268323328 |
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| author | Min, Pan Yujie, Wang Kaige, Hu Huiqiu, Deng |
| author_facet | Min, Pan Yujie, Wang Kaige, Hu Huiqiu, Deng |
| contents | Ternary hydrides have emerged as the primary focus of the new wave of research into superconducting hydrides. In this work, Mg-Ti-H ternary hydrides are explored under high pressures up to 300 GPa using the prediction method of the particle swarm optimization algorithm combined with first-principles calculations. Two new structures, $P4/nmm$-MgTiH$_6$ and $Pmm2$-Mg$_3$TiH$_6$, are identified to be thermodynamically stable at both 200 GPa and 300 GPa. Thermodynamically stable structures of Mg$_3$TiH$_{12}$ are also identified, whose space groups are $R3/m$ at 200 GPa and $Pm\bar{3}m$ at 300 GPa, respectively. Among these Mg-Ti-H structures, $P4/nmm$-MgTiH$_6$ achieves a record-high $T_\text{c}$ of 81.9 K at 170 GPa, exceeding the boiling point of liquid nitrogen. Such a high $T_\text{c}$ is primarily attributed to strong electron-phonon coupling (EPC) driven by low-frequency acoustic phonon modes, with the EPC strength reaching a large value of 1.54. The $T_\text{c}$ of $Pm\bar{3}m$-Mg$_3$TiH$_{12}$ is predicted to be 40 K at 300 GPa. Furthermore, element substitution of Zr(Hf) for Ti achieves considerable enhancement of superconducting properties in our predicted hydrogen-rich and high-symmetric crystal structures, i.e., $P4/nmm$-MgTiH$_6$ and $Pm\bar{3}m$-Mg$_3$TiH$_{12}$. The high pressure required for dynamical stability is lowered to 100 GPa in both $Pm\bar{3}m$-Mg$_3$ZrH$_{12}$ and $Pm\bar{3}m$-Mg$_3$HfH$_{12}$, and to 90 GPa and 120 GPa for $P4/nmm$-MgZrH$_6$ and $P4/nmm$-MgHfH$_6$, respectively. Particularly, the electronic structure near the Fermi level is significantly modified in the $P4/nmm$-MgHfH$_6$ phase, and pronounced softening of low-frequency acoustic phonon modes occurs. As a result, the EPC strength is enhanced to 1.72, leading to a higher $T_\text{c}$ of 86 K. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2602_07427 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | First-principles study on the high-$T_\text{c}$ superconductivity of Mg-Ti-H ternary hydrides up to the liquid-nitrogen temperature range under high pressures Min, Pan Yujie, Wang Kaige, Hu Huiqiu, Deng Materials Science Superconductivity Ternary hydrides have emerged as the primary focus of the new wave of research into superconducting hydrides. In this work, Mg-Ti-H ternary hydrides are explored under high pressures up to 300 GPa using the prediction method of the particle swarm optimization algorithm combined with first-principles calculations. Two new structures, $P4/nmm$-MgTiH$_6$ and $Pmm2$-Mg$_3$TiH$_6$, are identified to be thermodynamically stable at both 200 GPa and 300 GPa. Thermodynamically stable structures of Mg$_3$TiH$_{12}$ are also identified, whose space groups are $R3/m$ at 200 GPa and $Pm\bar{3}m$ at 300 GPa, respectively. Among these Mg-Ti-H structures, $P4/nmm$-MgTiH$_6$ achieves a record-high $T_\text{c}$ of 81.9 K at 170 GPa, exceeding the boiling point of liquid nitrogen. Such a high $T_\text{c}$ is primarily attributed to strong electron-phonon coupling (EPC) driven by low-frequency acoustic phonon modes, with the EPC strength reaching a large value of 1.54. The $T_\text{c}$ of $Pm\bar{3}m$-Mg$_3$TiH$_{12}$ is predicted to be 40 K at 300 GPa. Furthermore, element substitution of Zr(Hf) for Ti achieves considerable enhancement of superconducting properties in our predicted hydrogen-rich and high-symmetric crystal structures, i.e., $P4/nmm$-MgTiH$_6$ and $Pm\bar{3}m$-Mg$_3$TiH$_{12}$. The high pressure required for dynamical stability is lowered to 100 GPa in both $Pm\bar{3}m$-Mg$_3$ZrH$_{12}$ and $Pm\bar{3}m$-Mg$_3$HfH$_{12}$, and to 90 GPa and 120 GPa for $P4/nmm$-MgZrH$_6$ and $P4/nmm$-MgHfH$_6$, respectively. Particularly, the electronic structure near the Fermi level is significantly modified in the $P4/nmm$-MgHfH$_6$ phase, and pronounced softening of low-frequency acoustic phonon modes occurs. As a result, the EPC strength is enhanced to 1.72, leading to a higher $T_\text{c}$ of 86 K. |
| title | First-principles study on the high-$T_\text{c}$ superconductivity of Mg-Ti-H ternary hydrides up to the liquid-nitrogen temperature range under high pressures |
| topic | Materials Science Superconductivity |
| url | https://arxiv.org/abs/2602.07427 |