Towards a practical pair density-functional theory for many-electron systems

被引:58
作者
Furche, F [1 ]
机构
[1] Univ Karlsruhe, Inst Phys Chem, D-76128 Karlsruhe, Germany
来源
PHYSICAL REVIEW A | 2004年 / 70卷 / 02期
基金
美国国家科学基金会;
关键词
D O I
10.1103/PhysRevA.70.022514
中图分类号
O43 [光学];
学科分类号
070207 ; 0803 ;
摘要
In pair density-functional theory, the only unknown piece of the energy is the kinetic energy T as a functional of the pair density P(x(1),x(2)). Although T [P] has a simpler structure than the Hohenberg-Kohn functional of conventional density-functional theory, computational requirements are still moderate. In the present work, a particularly convenient model system to represent many-electron pair densities is introduced. This "boson pair model" (BPM) approximately treats electron pairs as noninteracting bosons. The resulting explicit model for the kinetic energy T-2[P] is shown to be exact for two-electron systems and a lower bound to T [P] for more than two electrons. The one- and two-particle density matrices obtained from the BPM yield upper bounds for the corresponding many-electron quantities. This suggests a partitioning T [P]=T-2[P]+T-eff [P], where only the remainder T-eff [P]greater than or equal to0 needs to be approximated. If the BPM is constrained to yield the exact ground-state pair density, a two-electron Schrodinger equation with an effective local two-particle potential results; the latter is identified as a sum of the bare Coulomb interaction and the functional derivative of T-eff [P]. This self-consistent scheme to minimize the energy with respect to P is more efficient than previous procedures. Further information on the functional derivative of T-eff [P] is derived from a contracted Schrodinger equation. Since T-eff [P] is explicitly known in the two-electron and noninteracting (Hartree-Fock) limits, the present method provides an alternative to density-matrix functional theories, which can be exact in the same limits and are similar in computational cost.
引用
收藏
页码:022514 / 1
页数:10
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