Structural, electronic and optical properties of the quasi-one-dimensional material ${\text{BaTiSe}}_3$ were investigated using density functional theory and were compared with that of ${\text{BaTiS}}_3$, which is well known for exhibiting the highest broadband giant birefringence. The relative stability of two different structures of ${\text{BaTiS}}_3$, one crystallizing in the space group $\text{P}{6}_3/\text{mmc}$ and another in $\text{P}{6}_3\text{mc}$ were studied using the PBE exchange-correlation functional. It was found that the recently synthesized $\text{P}{6}_3\text{mc}$ structure is more stable than the $\text{P}{6}_3/\text{mmc}$ structure. Electronic structure calculations with HSE06 and DFT + U methods predicted that both ${\text{BaTiS}}_3$ and ${\text{BaTiSe}}_3$ are narrow band gap semiconductors. These calculations also showed that ${\text{BaTiS}}_3$ is a direct band gap semiconductor while ${\text{BaTiSe}}_3$ is an indirect band gap semiconductor. Calculations of optical properties using the DFT + U method for different U values showed that both materials exhibit giant optical anisotropy. Birefringence of both materials were calculated and compared with experimental results of ${\text{BaTiS}}_3$. It was found that ${\text{BaTiSe}}_3$ exhibits broadband giant birefringence at least of the order of that exhibited by ${\text{BaTiS}}_3$.

准一维材料的结构，电子和光学性质 ${\text{钛酸钡}}_3$ 使用密度泛函理论进行了研究，并与 ${\text{钛酸钡}}_3$，以展现最高的宽带巨双折射而闻名。两种不同结构的相对稳定性${\text{钛酸钡}}_3$，一个在空间群中结晶的 $\text{P}{6}_3/\text{多媒体卡}$ 另一个在 $\text{P}{6}_3\text{mc}$使用PBE交换相关函数进行了研究。发现最近合成的$\text{P}{6}_3\text{mc}$ 结构比 $\text{P}{6}_3/\text{多媒体卡}$结构体。使用HSE06和DFT + U方法进行电子结构计算可预测两者${\text{钛酸钡}}_3$ 和 ${\text{钛酸钡}}_3$是窄带隙半导体。这些计算还表明${\text{钛酸钡}}_3$ 是直接带隙半导体，而 ${\text{钛酸钡}}_3$是一种间接的带隙半导体。使用DFT + U方法对不同的U值进行光学性能计算，结果表明两种材料均表现出巨大的光学各向异性。计算了两种材料的双折射并与实验结果进行了比较。${\text{钛酸钡}}_3$。发现${\text{钛酸钡}}_3$ 展现出的宽带巨双折射至少是由 ${\text{钛酸钡}}_3$。