For the interpretation of spectra of magnetic stellar objects such as magnetic white dwarfs (WDs), highly accurate quantum chemical predictions for atoms and molecules in finite magnetic field are required. Especially the accurate description of electronically excited states and their properties requires established methods such as those from coupled-cluster (CC) theory. However, respective calculations are computationally challenging even for medium-sized systems. Cholesky decomposition (CD) techniques may be used to alleviate memory bottlenecks. In finite magnetic field computations, the latter are increased due to the reduction of permutational symmetry within the electron-repulsion-integrals (ERIs) as well as the need for complex-valued data types. CD enables a memory-efficient, approximate description of the ERIs with rigorous error control and thus the treatment of larger systems at the CC level becomes feasible. In order to treat molecules in a finite magnetic field, we present in this work the working equations of the left and right-hand side equations for finite field (ff)-EOM-CD-CCSD for various EOM flavours as well as for the approximate ff-EOM-CD-CC2 method. The methods are applied to the study of the modification of the spectral lines of a magnesium transition by a helium atmosphere that can be found on magnetic WD stars.

中文翻译：

---

有限场 Cholesky 分解耦合簇技术 （ff-CD-CC）：He 大气和强磁场对 Mg 压力展宽的理论和应用


为了解释磁性恒星天体（如磁性白矮星 （WD））的光谱，需要对有限磁场中的原子和分子进行高精度的量子化学预测。特别是，准确描述电子激发态及其性质需要既定的方法，例如耦合簇 （CC） 理论中的方法。然而，即使对于中型系统，相应的计算在计算上也具有挑战性。Cholesky 分解 （CD） 技术可用于缓解内存瓶颈。在有限磁场计算中，由于电子排斥积分 （ERI） 内排列对称性的减少以及对复值数据类型的需求，后者会增加。CD 能够通过严格的错误控制对 ERI 进行内存高效的近似描述，因此在 CC 级别处理更大的系统变得可行。为了在有限磁场中处理分子，我们在这项工作中提出了各种 EOM 风格的有限场 （ff）-EOM-CD-CCSD 以及近似 ff-EOM-CD-CC2 方法的左侧和右侧方程的工作方程。这些方法应用于研究磁 WD 星上氦气气氛对镁跃迁光谱线的修改。