Embedded wavefunctions for 2D and 3D periodic molecular systems

尽管发展了不同的方法，但在周期系统中使用相关波函数仍然是一个挑战。本申请旨在能够使用相关波函数方法准确描述周期性分子系统中的局部性质，例如分子晶体中的局部缺陷或有机半导体中的基于跳跃的输运。虽然波函数方法提供了所需的动态或静态相关的精度，传统方法的计算成本与系统的大小显着缩放，特别是限制在实践中的分子固体和液体的波函数方法的应用。冻结密度嵌入（FDE）使准线性标度与子系统的数量，极大地促进了包括缺陷的局部性质的研究。在本申请中，使用局部高斯基的嵌入波函数将在2D和3D周期系统中与快速多极方法结合使用，以获得远程库仑贡献。冻融迭代用于松弛紧邻扰动或缺陷的分子。所提出的方法允许特别是避免缺陷的周期性重复，从而提供了一个完全放松的自洽描述的体相和表面使用相关的波函数。这种方法能够描述长程静电效应，例如局部激发态，但除了简单的静电模型，它还确保了排斥的贡献，由于在短距离的有效嵌入势，使分子内和分子间的影响充分占。新开发的方法特别适用于有机半导体材料，如四氮杂过氧芘（TAPPs），但也可用于研究溶质的局部性质。

Despite the development of different approaches, the use of correlated wave functions in periodic sys- tems is still a challenge. The present application aims to enable accurate description of local properties in periodic molecular systems, such as local defects in molecular crystals or hopping-based transport in or- ganic semiconductors, using correlated wavefunction methods. While wavefunction methods provide the required accuracy for dynamic or static correlation, the computational cost of conventional approaches scales significantly with system size, limiting in particular the application of wavefunction methods to molecular solids and liquids in practice. Frozen-density embedding (FDE) enables quasi-linear scaling with number of subsystems, greatly facilitating the study of local properties including defects. In the present application, embedded wavefunctions using a local Gaussian basis will be used in 2D and 3D periodic systems in combination with fast multipole methods for the long-range Coulomb contributions. Freeze-Thaw iterations are used to relax molecules in close proximity to perturbations or defects. The proposed approach allows in particular to avoid the periodic repetition of the defect, thus providing a fully relaxed self-consistent description of the bulk phase and surfaces using correlated wave functions. This approach is able to describe long-range electrostatic effects on e.g. local excited states, but in addition to simple electrostatic models it also ensures repulsion contributions due to the effective embedding poten- tial at short distances, so that both intramolecular and intermolecular effects are adequately accounted for. The newly developed methods are particularly applicable to organic semiconductor materials such as tetra-aza-peropyrenes (TAPPs), but can also be used to study local properties of solutes.