密度泛函理论与Hartree-Fock方法——混合处理中的稳态相关能校正

Stationary Correlation Energy in the Hybrid Approach of Density Functional Theory and Hartree - Fock Method

本文分析了通常的Hartree Fock(HF)相关能定义和密度泛函理论(DFT)中的相关能定义的等价性条件.认为在参考电子密度与真实密度相差很大时两种定义是不等价的,严格的DFT相关能比HF相关能(绝对值)要大.而在DFT与HF混合处理中得到的相关能比HF相关能(绝对值)要小,两者之差相当于稳态相关能.实际计算表明,通过合理地选择组态,采用有限Cl可以求得这一差值.本文描绘了双原子分子H_2(X^1∑_g^1),HF(X^1∑^+),N_2(X^1∑_g^+)的势能曲线,结果比完全CISD和MP4的曲线还要好.H_2的离解能是0.17a.u.,逼近实验值0.1747a.u..

The equivalence condition of the correlation energy definition in Hartree - Fock method (HF) and in Density Functional Theory (DFT) is analyzed. It is shown that when the reference electron density is far from the actual density of the system concerned, two definitions don' t give the same values and the DFT correlation energy is larger than the HF one in magnitude. Meanwhile, the correlation energy calculated by the hybrid approach of DFT and HF is smaller than the HF value in magnitude, the difference being explained by the stationary correlation energy. It is also verified that the difference can be estimated by limited CI method withappropriate configurations. The potential curves of several diatomic molecules H2 (X1∑g+ ), HF(X1∑+ ), N2 (X1∑g+ ) are computed, all are better than those by CISD or MP4 method. Furthermore, the calculated dissociation energy of H2 is 0. 17a. u. , in agreement with the experimental value, 0.1747a. u. .