The (001) surface of the emerging photovoltaic material cesium lead triiodide (CsPbI3) is studied. Using first-principles methods, we investigate the atomic and electronic structure of cubic (α) and orthorhombic (γ) CsPbI3. For both phases, we find that CsI-termination is more stable than PbI2-termination. For the CsI-terminated surface, we then compute and analyze the surface phase diagram. We observe that surfaces with added or removed units of nonpolar CsI and PbI2 are most stable. The corresponding band structures reveal that the α phase exhibits surface states that derive from the conduction band. The surface reconstructions do not introduce new states in the bandgap of CsPbI3, but for the α phase, we find additional surface states at the conduction band edge.

中文翻译：

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三碘化铯铅表面的原子和电子结构。

研究了新兴的光伏材料三碘化铯铯（CsPbI3）的（001）表面。使用第一原理方法，我们研究了立方（α）和正交（γ）CsPbI3的原子和电子结构。对于这两个阶段，我们发现CsI端接比PbI2端接更稳定。然后，对于CsI终止的表面，我们计算并分析表面相图。我们观察到，添加或删除非极性CsI和PbI2单元的表面最稳定。相应的能带结构表明，α相表现出源自导带的表面态。表面重建不会在CsPbI3的带隙中引入新的状态，但是对于α相，我们在导带边缘发现了其他表面状态。