First-principles calculations of electronic properties, surface stability and photocatalytic potentials of seleno-germanates A2GeSe4 (A = Mg; γ-Sr) surfaces for a promising visible light photocatalytic application,Materials Today Communications

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First-principles calculations of electronic properties, surface stability and photocatalytic potentials of seleno-germanates A2GeSe4 (A = Mg; γ-Sr) surfaces for a promising visible light photocatalytic application
Materials Today Communications ( IF 3.8 ) Pub Date : 2020-12-03 , DOI: 10.1016/j.mtcomm.2020.101799
Abdu Barde , Daniel P. Joubert

The four low-index, (100), (101), (110) and (111) surfaces of the A $_{2}$ GeSe $_{4}$ (A = Mg; $γ$ -Sr) seleno-germanates were studied using the first principles generalised gradient density functional theory approximation. From the optimized surfaces structures, surface stabilities were established by calculating the surface energies. Our calculation reveals that the Mg $_{2}$ GeSe $_{4}$ (101) and $γ$ -Sr $_{2}$ GeSe $_{4}$ (111) surfaces are the most energetically stable surfaces, for the two compounds, respectively. On the Mg $_{2}$ GeSe $_{4}$ (101) and $γ$ -Sr $_{2}$ GeSe $_{4}$ (111) most stable surface, the electronic properties, charge density, electrostatic potential, work function, band gap center and band-edge potentials were calculated. Calculated electronic density of state reveal for Mg $_{2}$ GeSe $_{4}$ (101) a metallic and $γ$ -Sr $_{2}$ GeSe $_{4}$ (111) a semiconductor surface. Analysis of total and partial density of state of surface compared to bulk reveals conduction band shifting toward valence band and exhibit surface electronic density state corresponding to $p$ -orbital of Se atom contribution around the Fermi-energy. Bader charge density analysis of the Mg $_{2}$ GeSe $_{4}$ (101) and $γ$ -Sr $_{2}$ GeSe $_{4}$ (111) surfaces reveals charge depletion around Mg, Sr and Ge atoms and charge accumulation around the Se atoms, which indicate covalent bonding between the Se and Ge, Mg and Sr atoms. The stable surfaces were used to calculate the electrostatic potential and thus determine the work function, band gap centre and band edges. The band edges compared to redox potential of water show that Mg $_{2}$ GeSe $_{4}$ (101) and $γ$ -Sr $_{2}$ GeSe $_{4}$ (111) surfaces suggest that are promising visible light photocatalytic materials

中文翻译：

硒代锗酸酯A的电子性质，表面稳定性和光催化势的第一性原理计算 $_{2}$ 锗硒 $_{4}$ （A =镁; $γ$ -Sr）表面有希望的可见光光催化应用

A的四个低折射率表面（100），（101），（110）和（111） $_{2}$ 锗硒 $_{4}$ （A =镁; $γ$ -Sr）硒锗酸酯使用第一个原理进行了广义梯度密度泛函理论逼近的研究。通过优化表面结构，通过计算表面能来建立表面稳定性。我们的计算表明，镁 $_{2}$ 锗硒 $_{4}$ （101）和 $γ$ -锶 $_{2}$ 锗硒 $_{4}$ （111）面分别是这两种化合物能量最稳定的表面。在镁上 $_{2}$ 锗硒 $_{4}$ （101）和 $γ$ -锶 $_{2}$ 锗硒 $_{4}$ （111）最稳定的表面，计算出电子性能，电荷密度，静电势，功函数，带隙中心和带边缘势。计算出的Mg的电子态密度 $_{2}$ 锗硒 $_{4}$ （101）金属和 $γ$ -锶 $_{2}$ 锗硒 $_{4}$ （111）半导体表面。分析表面状态的总密度和部分密度与体积相比，发现导带向价带移动，并表现出与 $p$ 费米能量附近的Se原子贡献的轨道。镁的较差电荷密度分析 $_{2}$ 锗硒 $_{4}$ （101）和 $γ$ -锶 $_{2}$ 锗硒 $_{4}$ （111）表面揭示Mg，Sr和Ge原子周围的电荷耗尽和Se原子周围的电荷积累，这表明Se与Ge，Mg和Sr原子之间存在共价键。稳定的表面用于计算静电势，从而确定功函数，带隙中心和带边缘。与水的氧化还原电位相比，能带边缘显示出Mg $_{2}$ 锗硒 $_{4}$ （101）和 $γ$ -锶 $_{2}$ 锗硒 $_{4}$ （111）表面表明有希望的可见光光催化材料

更新日期：2020-12-03

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