Correlations Among Atomic Electrons. E-book. Formato PDF Meyer Katzper   -  Forgotten Books, 2017  - 

The wave function obtained in this manner may give fairly good values for the energy but poor approximations to the true ground state wave function. The reason for the aforementioned is that in using the variational principle first order errors in the trial function produce only second order errors in the energy. To obtain a realistic wave function spatial correlation effects must be considered.