In this paper, the results of the first principles calculations within the framework of the density functional theory of the electronic spectrum of a GeS crystal are presented. The density of states and interband optical transitions are investigated. It was found that GeS compounds have semiconducting properties with a bandgap of 1.52 eV. The main contribution of the bands in the vicinity of the Fermi level is from the 3p and 3s states of the S and Ge atoms, respectively. The highest amplitude, about 2.3 eV (𝜀⊥), is mainly associated with the interband optical transitions between the states S(p) + Ge(s) →Ge(p) + S(s). The results of the luminescence studies of GeS and GeS:Gd layered crystals at room-temperature are presented. A noticeable increase in the intensity of the luminescence radiation in GeS:Gd has been established. The reason for the increase in the effectiveness of photoluminescence is due to the overlapping of optical transitions of GeS at 695 nm wavelength with the radiation lines of Gd3+ion at that same energy.

中文翻译：

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GeS 和 GeS:Gd 的电子和光学性质

本文介绍了在 GeS 晶体电子光谱的密度泛函理论框架内的第一性原理计算结果。研究了状态密度和带间光学跃迁。发现GeS化合物具有半导体特性，带隙为1.52 eV。费米能级附近能带的主要贡献来自 3p和 3s分别为 S 和 Ge 原子的状态。最高振幅，约 2.3 eV (𝜀⊥), 主要与状态之间的带间光学跃迁有关小号(p) + 葛(s) →葛(p) + 小号(s). 介绍了 GeS 和 GeS:Gd 层状晶体在室温下的发光研究结果。已确定 GeS:Gd 中的发光辐射强度显着增加。光致发光效率提高的原因是由于 GeS 在 695 nm 波长处的光学跃迁与 Gd 的辐射线重叠3+相同能量的离子。