Keivanloo Mohammad, Sandoghchi Mohammad, Mohammadizadeh Mohammad Reza, Kawamura Mitsuaki, Raebiger Hannes, Hongo Kenta, Maezono Ryo, Khazaei Mohammad
Department of Physics, University of Tehran, North Kargar Ave, Tehran 14395547, Iran.
Superconductivity Research Laboratory (SRL), Department of Physics, University of Tehran, North Kar-gar Ave., Tehran 14395547, Iran.
Nanoscale. 2025 Feb 27;17(9):5341-5349. doi: 10.1039/d4nr04231j.
In recent years, MAX phases and their two-dimensional counterparts, MXenes, have emerged as significant subjects of interest in the fields of science and engineering, owing to their varied geometries, compositions, and extensive range of applications. This research employs first-principles calculations to explore the geometrical structures, electronic characteristics, phonon dispersions, dynamic stability, electron-phonon coupling (EPC), and superconducting properties of 27 out-of-plane ordered double transition metal carbides, referred to as o-MAX phases, characterized by the general formula MM'AlC (where M = Nb, Mo, W and M' = Sc, Ti, Zr, Hf, V, Nb, Ta, Mo, W). We have identified 16 superconducting o-MAX phases, with four specific compounds WVAlC, WNbAlC, WTaAlC, and MoNbAlC exhibiting a critical temperature () that surpasses 10 K, representing the highest reported experimentally for MAX phases thus far. The calculated EPC constants for these materials are 0.98, 0.99, 1.02, and 0.74, correlating with values of 17.9, 14.8, 14.5, and 11 K, respectively. Remarkably, the predicted transition temperature of 17.9 K stands as the highest theoretically anticipated for any MAX phase to date. We conduct a thorough analysis of the specific mechanisms that facilitate superconductivity in these o-MAX systems. Our findings suggest that the presence of Kohn anomalies in low-frequency modes enhances electron-phonon interactions, resulting in increased superconducting transition temperatures (). Additionally, our results indicate that NbM'AlC compounds do not display superconducting behavior.
近年来，MAX相及其二维对应物MXenes，由于其多样的几何结构、组成和广泛的应用范围，已成为科学和工程领域中备受关注的重要课题。本研究采用第一性原理计算方法，探索了27种面外有序双过渡金属碳化物（称为o-MAX相）的几何结构、电子特性、声子色散、动态稳定性、电子-声子耦合（EPC）和超导特性，其通式为MM'AlC（其中M = Nb、Mo、W，M' = Sc、Ti、Zr、Hf、V、Nb、Ta、Mo、W）。我们已经确定了16种超导o-MAX相，其中四种特定化合物WVAlC、WNbAlC、WTaAlC和MoNbAlC的临界温度（）超过10 K，这是迄今为止MAX相实验报道的最高值。这些材料计算得到的EPC常数分别为0.98、0.99、1.02和0.74，分别对应于17.9 K、14.8 K、14.5 K和11 K的值。值得注意的是，预测的17.9 K转变温度是迄今为止任何MAX相理论上预期的最高值。我们对这些o-MAX系统中促进超导性的具体机制进行了深入分析。我们的研究结果表明，低频模式中存在的科恩反常增强了电子-声子相互作用，导致超导转变温度（）升高。此外，我们的结果表明，NbM'AlC化合物不表现出超导行为。
