几种交换能密度泛函的数值检验

通过对原子和分子体系的密度泛函计算检验了LDA、B88、BR89、B2000、VSX和作者提出的CPX等6种交换能密度泛函的精度。非定域校正使原子的交换能计算值有很大改善，其中用B88和CPX泛函的计算结果最好。对于只含轻元素的分子，除LDA泛函以外，用其他泛函计算的原子化能都比较好，接近或者稍微超过MP2方法的计算精度。对于含重元素的分子，原子化能的计算误差显著增大，B88、CPX和BR89泛函给出的结果比较好一些；VSX泛函的精度还不如不加梯度校正的LDA泛函。非定域校正并不改善第一电离势的计算结果。VSXC泛函虽然用于只含轻元素分子的计算比较成功，用于含重元素体系计算效果很差。作者提出的CPX泛函的表现还比较好，通过仔细优选参数，有可能发展成为一种对含重元素体系计算精度也较高的交换能密度泛函。

Numerical Examination of Several Exchange Energy Functionals

The accuracy of several density functionals for exchange energy (LDA,B88,BR89,B2000,VSX and CPX,a composite functional proposed in the present paper) has been examined through the calculation of a series of atoms and molecules by means of DFT method with different exchange potential functionals.The following conclusion can be drawn.The nonlocal correction improves significantly the calculated exchange energies for atoms,among them the functional B88 and CPX give the best results.For the molecules containing only light elements all examined exchange energy functionals,except LDA,give satisfactory atomization energies.The calculation accuracy is approximately equal to or better than that of MP2 approach.However,for the molecules containing heavy elements the error of the calculated atomization energies increases significantly in all cases,only the functionals B88,CPX and BR89 give relatively reliable results.The results calculated with the functionals VSX are even worse than those calculated with LDA.The nonlocal correction does not improve the calculated results of the first ionization potentials.Although the functional VSXC is successful when it is applied to the systems containing only light elements,its performance is bad when heavy elements are involved in the systems under consideration.The functional CPX shows pretty good performance.It seems possible to develop an exchange energy functional with high accuracy even for the calculation of heavy-elements containing systems through carefully optimizing the parameters involved in the functional CPX or some other composite exchange energy functionals.