Derikvandi Zahra, Dadsetani Mehrdad, Nejatipour Reihan
Department of Physics, Lorestan University, Khoramabad, Islamic Republic of Iran.
Department of Physics, Lorestan University, Khoramabad, Islamic Republic of Iran.
Micron. 2023 Sep;172:103488. doi: 10.1016/j.micron.2023.103488. Epub 2023 Jun 1.
In this study, the effect of the termination groups (T = F, OH, O) on the energy loss near edge structure (ELNES) of carbon K edge in MoC MXene at orientation-independent conditions has been investigated using first-principles calculations based on the full-potential linearized augmented plane wave (FP-LAPW) method. The results show that within the YS-PBE0 functional, the MoCF is a semiconductor with an indirect band gap of 0.723 eV. For MoCO, the indirect band gap increases to 0.17 eV within the screened hybrid functional. The calculation results of ELNES spectra with the affection of core-hole show that, in comparison to pristine MoC, as a fingerprint of termination groups, the spectral structures in MoCT are reproduced at higher energies. Moreover, the spectral features of MoCT are sensitive to the chemical nature and the location of the T groups on the pristine MoC MXene surface. When going from T = O to T = F and, further, to T = OH, the energy separation between the main peaks increases, which is a sign of decreasing the Mo-C bond length, respectively, from T = O to T = F and to T = OH. The comparison of ELNES spectra and the unoccupied densities of states (DOS) reveal that, the origin of the first structure at the carbon K edge of MoCT is mostly result from electron transition to p state, while in pristine MoC, mainly due to the transition to p + p state. Other structures at higher energies mainly arise from electron transitions to p + p state and partially to p state. The spectral decomposition of the ELNES into in-plane (l' = 1, m' = ± 1) and out-of-plane (l' = 1, m' = 0) components also confirms these results. Generally, in both MoC and MoCT, the contribution of in-plane element in most of the structures is more considerable.
在本研究中，基于全势线性缀加平面波（FP-LAPW）方法，通过第一性原理计算，研究了终止基团（T = F、OH、O）在与取向无关的条件下对MoC MXene中碳K边近边结构能量损失（ELNES）的影响。结果表明，在YS-PBE0泛函内，MoCF是一种间接带隙为0.723 eV的半导体。对于MoCO，在筛选后的杂化泛函内，间接带隙增加到0.17 eV。考虑芯孔影响的ELNES光谱计算结果表明，与原始MoC相比，作为终止基团的指纹，MoCT中的光谱结构在更高能量处重现。此外，MoCT的光谱特征对原始MoC MXene表面上T基团的化学性质和位置敏感。当从T = O变为T = F，再变为T = OH时，主峰之间的能量间隔增加，这分别是从T = O到T = F以及到T = OH时Mo - C键长减小的标志。ELNES光谱与未占据态密度（DOS）的比较表明，MoCT碳K边第一个结构的起源主要是电子跃迁到p态，而在原始MoC中，主要是由于跃迁到p + p态。更高能量处的其他结构主要源于电子跃迁到p + p态以及部分跃迁到p态。将ELNES光谱分解为面内（l' = 1，m' = ±1）和面外（l' = 1，m' = 0）分量也证实了这些结果。一般来说，在MoC和MoCT中，面内元素在大多数结构中的贡献都更为显著。
