密度泛函计算条件对结果精度的影响

通过对有代表性的分子BCl₃,SO₂,ZnO,TiCl₄,LuF₃的一系列计算,从三个方面考察密度泛函理论的Kohn-Sham方法中采用的计算条件对结果精度的影响.发现基组完备性对计算结果影响最大,数值积分取点数目对计算结果影响略小.电荷多极投影收敛较快.分子几何构型和振动基频对计算条件不太敏感,总能量和键能对计算结果较敏感.在计算键能时对分子及其组成原子采用相同的基组和积分布点方式可以减少误差.选择适当的计算条件,用较小的计算量可以得到与现有近似能量密度泛函精度相匹配的结果.

Influence of the Computation Conditions on the Results in Density Functional Calculations

The influence of the computation conditions on the results in the calculations with Kohn-Sham density functional theory has been studied through a series of calculations on the molecules with various compositions and structures such as BCl_3, SO_2, ZnO, TiCl_4, LuF_3. Three factors are considered. It is found that the completeness of the basis sets is the most important factor. The number of the grid points of the numerical integration is less important. The projection for decomposing the molecular charge into multipolar components centered in each atomic nucleus converges fairly rapidly. The molecular geometry and the fundamental vibrational frequency are insensitive to the computation conditions, while the total energy and bond energy are pretty sensitive. If the same basis set and the same numerical integration points are used for a molecule and its constituting atoms in calculating its bond energy, the error of the calculated result could be reduced. It is shown that the calculation results with an accuracy matched with the approximate DFT formulas can be obtained by choosing the mediate computation conditions with a smaller computational effort.