The structural, electronic, and magnetic properties of VSSe, VSeTe, and VSTe monolayers in both 2H and 1T phases are investigated via first-principles calculations. The 2H phase is energetically favorable in VSSe and VSeTe, whereas the 1T phase is lower in energy in VSTe. For V-based Janus monolayers in the 2H phase, calculations of the magnetic anisotropy show an easy-plane for the magnetic moment. As such, they should not exhibit a ferromagnetic phase transition, but instead, a Berezinskii-Kosterlitz-Thouless (BKT) transition. A classical XY model with nearest-neighbor coupling estimates critical temperatures (${\mathrm{T}}_{\text{BKT}}$) ranging from 106 K for VSSe to 46 K for VSTe.

中文翻译：

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钒基Janus二硫化碳单分子膜的结构，电子和磁性：第一性原理研究

通过第一性原理计算，研究了2H和1T相中VSSe，VSeTe和VSTe单层的结构，电子和磁性。在VSSe和VSeTe中2H相在能量上有利，而在VSTe中1T相的能量较低。对于2H相中基于V的Janus单层，磁各向异性的计算显示出磁矩的易平面。因此，它们不应表现出铁磁相变，而应表现出Berezinskii-Kosterlitz-Thouless（BKT）跃迁。具有近邻耦合的经典XY模型估计临界温度（${\mathrm{Ť}}_{\text{BKT}}$）范围从VSSe的106 K到VSTe的46K。