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首页> 外文期刊>RSC Advances >Dimension-dependent band alignment and excitonic effects in graphitic carbon nitride: a many-body perturbation and time-dependent density functional theory study
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Dimension-dependent band alignment and excitonic effects in graphitic carbon nitride: a many-body perturbation and time-dependent density functional theory study

机译：石墨氮化碳中尺寸相关的能带排列和激子效应：多体扰动和时间相关的密度泛函理论研究

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摘要

First-principles many-body theory and time-dependent density functional theory were used to study the dimension effects on the band alignment and optical properties of s-triazine and graphitic C3N4. The inclusion of quasiparticle corrections is very important to describe the quantum confinement and the enhancement of the electron–electron (e–e) interaction. The calculated quasiparticle gaps range from 4.0 eV (monolayer) to 3.21 eV (tetralayer). The position of the valence band maxima is found to be almost constant, whereas the conduction band minima show a strong quantum confinement effect with a variation of ～0.7 eV respective to the bulk structure. The calculated frequency-dependent imaginary part of the dielectric function using the Bethe–Salpeter equation shows prominent excitonic effects, where there is a strong redistribution of the spectral weight to lower photon energies in the ultraviolet frequencies where the major part of the absorption occurs. On the other hand, a less intense excitonic absorption in the visible region is due to light polarization perpendicular to the surface plane. In contrast, time-dependent density functional theory also shows a redistribution of the spectral weight in the ultraviolet but it fails to describe the excitonic features in the visible region.
机译：用第一性原理多体理论和时变密度泛函理论研究尺寸对 s -三嗪和石墨C 3 < / sub> N 4 。包括准粒子校正对于描述量子约束和增强电子-电子（e-e）相互作用非常重要。计算的准粒子间隙范围为4.0 eV（单层）至3.21 eV（四层）。价带最大值的位置被发现几乎是恒定的，而导带最小值则显示出强的量子约束效应，其相对于整体结构的变化约为〜0.7 eV。使用Bethe–Salpeter方程计算的介电函数随频率变化的虚部显示出显着的激子效应，在光谱吸收中，光谱权重强烈地分配给较低的光子能量，而紫外光发生了吸收的主要部分。另一方面，在可见光区域中较少的激子吸收是由于垂直于表面平面的光偏振引起的。相反，随时间变化的密度泛函理论也显示了紫外光谱权重的重新分布，但未能描述可见光区域的激子特征。

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