Experimental realization of single-layer MoSi₂N₄ is among the latest groundbreaking advances in the field of two-dimensional (2D) materials. Inspired by this accomplishment, herein we conduct first-principles calculations to explore the stability of MC₂N₄ (M = Cr, Mo, W, V, Nb, Ta, Ti, Zr, Hf) monolayers. Acquired results confirm the desirable thermal, dynamical, and mechanical stability of MC₂N₄ (M = Cr, Mo, W, V) nanosheets. Interestingly, CrC₂N₄, MoC₂N₄, and WC₂N₄ monolayers are found to be semiconductors with band gaps of 2.32, 2.76, and 2.86 eV, respectively, using the HSE06 functional, whereas VC₂N₄ lattice shows a metallic nature. The direct gap semiconducting nature of the CrC₂N₄ monolayer results in excellent absorption of visible light. The elastic modulus and tensile strength of the CrC₂N₄ nanosheet are predicted to be remarkably high, 676 and 54.8 GPa, respectively. On the basis of iterative solutions of the Boltzmann transport equation, the room temperature lattice thermal conductivity of the CrC₂N₄ monolayer is predicted to be 350 W/mK, among the highest in 2D semiconductors. CrC₂N₄ and WC₂N₄ lattices are also found to exhibit outstandingly high piezoelectric coefficients. This study introduces the CrC₂N₄ nanosheet as a novel 2D semiconductor with outstandingly high mechanical strength, thermal conductivity, carrier mobility, and piezoelectric coefficient.

单层 MoSi ₂ N _{4 的}实验实现是二维 (2D) 材料领域的最新突破性进展之一。受这一成就的启发，我们在此进行第一性原理计算以探索 MC ₂ N ₄ (M = Cr、Mo、W、V、Nb、Ta、Ti、Zr、Hf) 单层的稳定性。获得的结果证实了 MC ₂ N ₄ (M = Cr、Mo、W、V) 纳米片所需的热、动力学和机械稳定性。有趣的是，CrC ₂ N ₄、MoC ₂ N ₄和WC ₂ N ₄发现单层是带隙分别为 2.32、2.76 和 2.86 eV 的半导体，使用 HSE06 功能，而 VC ₂ N ₄晶格显示金属性质。CrC ₂ N ₄单层的直接间隙半导体性质导致对可见光的极好吸收。CrC ₂ N ₄纳米片的弹性模量和拉伸强度预计非常高，分别为676 和54.8 GPa。基于玻尔兹曼输运方程的迭代解，CrC ₂ N ₄的室温晶格热导率预计单层为 350 W/mK，是二维半导体中最高的。CrC ₂ N ₄和WC ₂ N ₄晶格也被发现表现出非常高的压电系数。本研究介绍了 CrC ₂ N ₄纳米片作为一种新型二维半导体，具有出色的机械强度、热导率、载流子迁移率和压电系数。