完全活性空间组态相互作用能量的拟合和外推

发布时间：2019-05-09 05:58

【摘要】：完全活性空间组态相互作用计算与完全活性空间中的活性电子数和活性轨道数有关,但完全活性空间组态相互作用的能量不是活性电子数和活性轨道数的单调递减函数,因此活性轨道数和活性电子数不能用来外推完全活性空间组态相互作用的能量。为此,我们定义了一个新的变量:活性空间中的最大未占满轨道数。我们对一系列单重态、双重态和三重态分子进行了完全活性空间组态相互作用的计算,并利用活性空间中的活性电子数和最大未占满轨道数这两个变量,对这些基态能量进行了拟合和外推,拟合的均方根误差都在10~(-6)数量级。外推能量的精度优于MP4,对小分子体系,其精度高于CCSD。外推的完全的组态相互作用(FCI)能量值和实际计算的FCI值也很接近。另外,我们还利用外推能量来优化双原子分子的平衡键长,并计算谐振频率,其精度优于CASSCF。
[Abstract]:The calculation of fully active space configuration interaction is related to the active electron number and active orbital number in fully active space, but the energy of fully active space configuration interaction is not the monotone decreasing function of active electron number and active orbital number. Therefore, the active orbital number and the active electron number can not be used to extrapolate the energy of the complete active space configuration interaction. For this reason, we define a new variable: the maximum number of unoccupied full orbitals in the active space. We calculate the fully active space configuration interaction of a series of singlet, duplet and triplet molecules, and make use of the active electron number and the maximum unoccupied full orbital number in the active space. The ground state energy is fitted and extrapolated, and the root mean square error of fitting is in the order of 10 ~ (- 6). The accuracy of extrapolation energy is better than that of MP4, for small molecular systems, and the accuracy of extrapolation energy is higher than that of CCSD.. The extrapolated complete configuration interaction (FCI) energy value is also very close to the actual calculated FCI value. In addition, we also use extrapolation energy to optimize the equilibrium bond length of diatomic molecules and calculate the resonance frequency. The accuracy is better than that of CASSCF..
【作者单位】：北京科技大学化学与生物工程学院化学与化学工程系功能分子与晶态材料科学与应用北京市重点实验室;
【基金】：国家自然科学基金(21173020,21473008)资助项目~~
【分类号】：O641.1

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