Department of Chemistry and Biochemistry, and Department of Physics, Texas Tech University, P.O. Box 41061, Lubbock, Texas 79409-1061, USA.
J Chem Phys. 2018 Mar 14;148(10):104101. doi: 10.1063/1.5017621.
Using a combination of ideas, the ground and several excited electronic states of the helium atom and the hydrogen molecule are computed to chemical accuracy-i.e., to within 1-2 mhartree or better. The basic strategy is very different from the standard electronic structure approach in that the full two-electron six-dimensional (6D) problem is tackled directly, rather than starting from a single-electron Hartree-Fock approximation. Electron correlation is thus treated exactly, even though computational requirements remain modest. The method also allows for exact wave functions to be computed, as well as energy levels. From the full-dimensional 6D wave functions computed here, radial distribution functions and radial correlation functions are extracted-as well as a 2D probability density function exhibiting antisymmetry for a single Cartesian component. These calculations support a more recent interpretation of Hund's rule, which states that the lower energy of the higher spin-multiplicity states is actually due to reduced screening, rather than reduced electron-electron repulsion. Prospects for larger systems and/or electron dynamics applications appear promising.
使用多种思想的组合，计算氦原子和氢分子的基态和几个激发电子态达到化学精度，即，误差在 1-2 毫哈特里以内或更好。基本策略与标准电子结构方法非常不同，因为直接解决了全两电子六维（6D）问题，而不是从单电子 Hartree-Fock 近似开始。因此，尽管计算要求仍然适度，但可以精确处理电子相关。该方法还允许计算精确的波函数以及能级。从这里计算出的全维 6D 波函数中，提取了径向分布函数和径向相关函数，以及一个二维概率密度函数，该函数在单个笛卡尔分量上表现出反对称性。这些计算支持 Hund 规则的更近期解释，该规则指出，较高自旋多重度态的较低能量实际上是由于屏蔽减少，而不是电子-电子排斥减少。对于更大系统和/或电子动力学应用，前景似乎很有希望。
