Electronic structures of iMAX phases and their two-dimensional derivatives: A family of piezoelectric materials
Electronic structures of iMAX phases and their two-dimensional derivatives: A family of piezoelectric materials
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DOI：
10.1103/physrevmaterials.2.074002
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发表时间：
2018-06
影响因子：
3.4
通讯作者：
M. Khazaei;V. Wang;C. Sevik;A. Ranjbar;M. Arai;S. Yunoki
中科院分区：
文献类型：
--
作者：
M. Khazaei;V. Wang;C. Sevik;A. Ranjbar;M. Arai;S. Yunoki
最近，一组MAX相，(Mo$_{2/3}$Y$_{1/3}$)$_2$Alc，(Mo$_{2/3}$SC$_{1/3}$)$_2$Alc，(W$_{2/3}$SC$_{1/3}$)$_2$Alc，(W$_{2/3}$Y$_{1/3}$)$_2$Alc，面内有序的双过渡金属，命名为IMAX相都是人工合成的。在实验上，其中一些MAX相可以被化学剥离成二维(2D)单层或多层过渡金属碳化物，即所谓的MXenes。因此，由IMAX相衍生的2D纳米结构被命名为iMXenes。在这里，我们研究了实验发现的IMAX相及其可能的iMXene衍生物的结构稳定性和电子结构。我们发现IMAX相及其原始的、F或OH端基的IMXenes是金属的。然而，在O终止时，(Mo${2/3}$Y${1/3}$)$2$C、(Mo${2/3}$SC${1/3}$)$2$C、(W${2/3}$Y${1/3}$)$2$C和(W${2/3}$SC${1/3}$)$2$C变为半导体。由于没有中心对称性，半导体iMXenes可能会在压电性方面得到应用。我们的计算表明，半导体iMXenes的巨压电系数高达45×10^-10$~C/m。
Recently, a group of MAX phases, (Mo$_{2/3}$Y$_{1/3}$)$_2$AlC, (Mo$_{2/3}$Sc$_{1/3}$)$_2$AlC, (W$_{2/3}$Sc$_{1/3}$)$_2$AlC, (W$_{2/3}$Y$_{1/3}$)$_2$AlC, and (V$_{2/3}$Zr$_{1/3}$)$_2$AlC, with in-plane ordered double transition metals, named iMAX phases, have been synthesized. Experimentally, some of these MAX phases can be chemically exfoliated into two-dimensional (2D) single- or multilayered transition metal carbides, so-called MXenes. Accordingly, the 2D nanostructures derived from iMAX phases are named iMXenes. Here, we investigate the structural stabilities and electronic structures of the experimentally discovered iMAX phases and their possible iMXene derivatives. We show that the iMAX phases and their pristine, F, or OH-terminated iMXenes are metallic. However, upon O termination, (Mo$_{2/3}$Y$_{1/3}$)$_2$C, (Mo$_{2/3}$Sc$_{1/3}$)$_2$C, (W$_{2/3}$Y$_{1/3}$)$_2$C, and (W$_{2/3}$Sc$_{1/3}$)$_2$C iMXenes turn into semiconductors. Owing to the absence of centrosymmetry, the semiconducting iMXenes may find applications in piezoelectricity. Our calculations reveal that the semiconducting iMXenes possess giant piezoelectric coefficients as large as 45$\times10^{-10}$~C/m.