The development of 2D materials with excellent electronic properties and piezoelectric response is clearly critical for multifunctional piezoelectric devices. Herein, based on first-principles calculations, the electronic, mechanical, and piezoelectric properties of a series of 2D copper-based ternary chalcogenides, denoted as CuMX₂ (M = Sb and Bi; X = S and Se) monolayers, are systematically studied, which can be obtained by exfoliating from their bulk counterparts. The calculations show that these ternary CuMX₂ monolayers exhibit desirable dynamical and thermal stabilities and moderate bandgaps. The calculated piezoelectric coefficients $d_{11}$ and $d_{12}$ of these monolayers are in the range of 0.44–6.14 and 9.13–29.52 pm V⁻¹, respectively, which exceed or approach those of most well-studied 2D systems. Interestingly, as compared with other reported 2D systems, the CuMX₂ monolayers exhibit an anomalous anisotropy of piezoelectric response, manifested as the larger coefficient $d_{12}$ than coefficient $d_{11}$. The study demonstrates that the CuMX₂ monolayers are potential 2D candidates in nanoelectric and nanopiezoelectric devices.

中文翻译：

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二维铜基三元硫属化物 CuMX2 压电响应的异常各向异性

开发具有优异电子性能和压电响应的二维材料对于多功能压电器件显然至关重要。在此，基于第一性原理计算，系统地研究了一系列二维铜基三元硫属化物，表示为 CuMX ₂（M = Sb 和 Bi；X = S 和 Se）单层的电子、机械和压电性能，可以通过从它们的大块对应物上剥落来获得。计算表明，这些三元 CuMX ₂单层表现出理想的动力学和热稳定性以及适中的带隙。计算出的压电系数$d_{11}$ 和 $d_{12}$这些单层分别在 0.44-6.14 和 9.13-29.52 pm V ^-1的范围内，超过或接近最深入研究的二维系统。有趣的是，与其他报道的二维系统相比，CuMX ₂单层表现出异常的压电响应各向异性，表现为较大的系数$d_{12}$ 比系数 $d_{11}$. 该研究表明，CuMX ₂单层是纳米电和纳米压电器件中潜在的二维候选材料。