Influence of high-energy local orbitals and electron-phonon interactions on the band gaps and optical absorption spectra of hexagonal boron nitride
Influence of high-energy local orbitals and electron-phonon interactions on the band gaps and optical absorption spectra of hexagonal boron nitride
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高能局域轨道和电子声子相互作用对六方氮化硼带隙和光吸收光谱的影响
DOI：
10.1103/physrevb.102.045117
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发表时间：
2020
影响因子：
3.7
通讯作者：
Li Xin-Zheng
中科院分区：
文献类型：
--
作者：
Shen Tong;Zhang Xiao-Wei;Shang Honghui;Zhang Min-Ye;Wang Xinqiang;Wang En-Ge;Jiang Hong;Li Xin-Zheng
我们报告的从头算能带图和六方氮化硼（$h$-BN）的光学吸收光谱，侧重于解开如何$GW$计算的基组的完整性和电子-声子相互作用（EPI）对他们的影响。基组的完整性，一个问题，这是很少讨论在以前的光学光谱计算的$h$-BN，被发现是至关重要的，在提供收敛的准粒子带隙。在三个不同的代码之间的比较中，我们表明，通过在基于$GW$的全电子线性缀加平面波计算中包括高能局域轨道，准粒子直接和基本间接带隙被加宽了$\ensuremath{\sim}0.2$ eV，在$G{W}_{0}$水平上分别给出6.81 eV和6.25 eV的值。另一方面，EPI使它们在0 K时分别降低到6.62 eV和6.03 eV，在300 K时分别降低到6.60 eV和5.98 eV。与钳位晶体结构，吸收光谱的第一个峰值是在6.07 eV，起源于直接激子的布里渊区周围的电子跃迁$K$贡献。在Bethe-Salpeter方程中加入EPIs重整化准粒子后，激子-声子耦合在300 K时将第一个峰移动到5.83 eV，低于实验值6.00$ eV.这种精度是可以接受的从头计算描述的激发态没有拟合参数。
We report ab initio band diagram and optical absorption spectra of hexagonal boron nitride ($h$-BN), focusing on unravelling how the completeness of the basis set for $GW$ calculations and electron-phonon interactions (EPIs) impact on them. The completeness of the basis set, an issue which was seldom discussed in previous optical spectra calculations of $h$-BN, is found crucial in providing converged quasiparticle band gaps. In the comparison among three different codes, we demonstrate that by including high-energy local orbitals in the all-electron linearized augmented plane waves based $GW$ calculations, the quasiparticle direct and fundamental indirect band gaps are widened by $\ensuremath{\sim}0.2$ eV, giving values of 6.81 eV and 6.25 eV, respectively at the $G{W}_{0}$ level. EPIs, on the other hand, reduce them to 6.62 eV and 6.03 eV respectively at 0 K, and 6.60 eV and 5.98 eV respectively at 300 K. With clamped crystal structure, the first peak of the absorption spectrum is at 6.07 eV, originating from the direct exciton contributed by electron transitions around $K$ in the Brillouin zone. After including the EPIs-renormalized quasiparticles in the Bethe-Salpeter equation, the exciton-phonon coupling shifts the first peak to 5.83 eV at 300 K, lower than the experimental value of $\ensuremath{\sim}6.00$ eV. This accuracy is acceptable to an ab initio description of excited states with no fitting parameter.