关键词: 密度泛函, 交换能, 理论计算, 含重元素体系

Abstract: 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 functinals, 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.

Key words: density functionals, exchange energy, theoretical calculations, systems containing heavy elements