The ternary rare-earth sulfides ALnS₂ have been widely applied in phosphors or scintillator materials. This study focused on systematically discussing the structural, electronic and optical properties of AGdS₂ (A = Li, Na, K, Rb and Cs) ternary gadolinium sulfides using First-principles calculations for a better understanding of the physical properties of AGdS₂. The ΔH values of all these sulfides reveal that they are phase stable, and LiGdS₂ has the best phase stability. Electronic properties, including band structure, DOS, electron density difference and Mulliken population, provide that these sulfides are indirect band-gap semiconductors and have strong Gd–S covalent bonds and weak A-S ionic-covalent mixed bonds. The calculated absorption coefficients and reflectivity indicate that these AGdS₂ sulfides are appropriate for the longer wavelength lasers. The anisotropy in optical properties for AGdS₂ sulfides was studied through the polycrystalline and directional static dielectric constants ε₁(0) and static refractive indexes n(0), and the order of optical anisotropy can be obtained as LiGdS₂ > NaGdS₂ > KGdS₂ > RbGdS₂ > CsGdS₂.

三元稀土硫化物ALnS ₂已广泛应用于磷光体或闪烁体材料中。这项研究集中于使用第一性原理计算系统地讨论AGdS ₂（A = Li，Na，K，Rb和Cs）三元，硫化物的结构，电子和光学性质，以便更好地理解AGdS ₂的物理性质。所有这些硫化物的ΔH值表明它们是相稳定的，并且LiGdS ₂具有最佳的相位稳定性。电子性质，包括能带结构，DOS，电子密度差和Mulliken种群，提供了这些硫化物是间接的带隙半导体，并具有强的Gd-S共价键和弱的AS离子共价混合键。计算得出的吸收系数和反射率表明，这些AGdS ₂硫化物适用于较长波长的激光器。用于AGDS在光学特性的各向异性_2个硫化物是通过多晶和定向静态介电常数研究ε ₁（0）和静态折射率Ñ（0），和光学各向异性的顺序可以根据LiGdS获得₂  > NaGdS ₂ > KGdS ₂  > RbGdS ₂  > CsGdS ₂。