${\left(\mathrm{BEDT}\text{−}\mathrm{TFF}\right)}_2{\mathrm{I}}_3$ charge transfer salts are reported to show superconductivity and pressure-induced quasi-two-dimensional Dirac cones at the Fermi level. By performing state of the art ab initio calculations in the framework of density functional theory, we investigate the structural and electronic properties of the three structural phases $\alpha$, $\beta$, and $\kappa$. We furthermore report about the irreducible representations of the corresponding electronic band structures, symmetry of their crystal structure, and the origin of band crossings. Additionally, we discuss the chemically induced strain in $\kappa \text{−}{\left(\mathrm{BEDT}\text{−}\mathrm{TTF}\right)}_2{\mathrm{I}}_3$ achieved by replacing the iodine layer with other halogens: fluorine, bromine, and chlorine. In the case of $\kappa \text{−}{\left(\mathrm{BEDT}\text{−}\mathrm{TTF}\right)}_2{\mathrm{F}}_3$, we identify topologically protected crossings within the band structure. These crossings are forced to occur due to the nonsymmorphic nature of the crystal. The calculated electronic structures presented here are added to the organic materials database (OMDB).

中文翻译：

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α-（BEDT-TTF）2I3，β-（BEDT-TTF）2I3和κ-（BEDT-TTF）2X3（X = I，F，Br，Cl）有机电荷转移盐的结构和电子性质

${（\mathrm{贝德}\text{-}\mathrm{TFF}）}_{\mathrm{2个}}{\mathrm{一世}}_3$据报道，电荷转移盐在费米能级表现出超导性和压力诱导的准二维狄拉克锥。通过在密度泛函理论的框架内进行最先进的从头计算，我们研究了三个结构相的结构和电子性质$\alpha$， $\beta$， 和 $\kappa$。我们还报告了相应的电子能带结构的不可约表示，它们的晶体结构的对称性以及能带穿越的起源。此外，我们讨论了化学诱导的菌株$\kappa \text{-}{（\mathrm{贝德}\text{-}\mathrm{特遣队}）}_{\mathrm{2个}}{\mathrm{一世}}_3$通过用其他卤素（氟，溴和氯）代替碘层可实现此目的。如果是$\kappa \text{-}{（\mathrm{贝德}\text{-}\mathrm{特遣队}）}_{\mathrm{2个}}{\mathrm{F}}_3$，我们确定了带状结构内受拓扑保护的交叉点。由于晶体的非对称性质，这些交叉被迫发生。此处显示的计算出的电子结构被添加到有机材料数据库（OMDB）中。