Theoretische Chemie, Fakultät für Chemie, Universität Bielefeld, Universitätsstr. 25, D-33615 Bielefeld, Germany.
J Chem Phys. 2017 Feb 14;146(6):064117. doi: 10.1063/1.4975662.
A multi-layer multi-configurational time-dependent Hartree (MCTDH) approach using a second quantization representation (SQR) based on optimized time-dependent orbitals is introduced. The approach combines elements of the multi-layer MCTDH-SQR approach of Wang and Thoss, which employs a preselected time-independent orbital basis, and the MCTDH for bosons and multi-configuration time-dependent Hartree-Fock approaches, which do not use multi-layering but employ time-dependent orbital bases. In contrast to existing MCTDH-type approaches, the results of the present approach for a given number of configurations are not invariant with respect to unitary transformations of the time-dependent orbital basis. Thus a natural orbital representation is chosen to achieve fast convergence with respect to the number of configurations employed. Equations of motion for the present ansatz, called (multi-layer) MCTDH in optimized second quantization representation, are derived. Furthermore, a scheme for the calculation of optimized unoccupied single-particle functions is given which can be used to avoid singularities in the equations of motion.
介绍了一种基于优化时变轨道的二次量子化（SQR）的多层多组态含时哈特里（MCTDH）方法。该方法结合了 Wang 和 Thoss 的多层 MCTDH-SQR 方法的元素，该方法采用了预选的时不变轨道基，以及不使用多层但采用时变轨道基的玻色子多组态含时哈特利-福克方法。与现有的 MCTDH 型方法不同，对于给定数量的组态，本方法的结果对于时变轨道基的幺正变换不具有不变性。因此，选择自然轨道表示来实现对所采用的组态数量的快速收敛。推导出了本假设的运动方程，称为（多层）优化二次量子化表示中的 MCTDH。此外，还给出了计算优化占据单粒子函数的方案，该方案可用于避免运动方程中的奇点。
