Chemistry Reference
In-Depth Information
always determined better than the wavefunction. The same is true for
the second-order energies of Chapter 10.
.
The variational method privileges the regions of space near the
nucleus, so that variationally determined wavefunctions may be not
appropriate for dealing with the expectation values of operators that
take large values far fromthe nucleus, like the electric dipolemoment.
Variational approximations to energy and the wavefunction can be
worked out simply by introducing some variational parameters {c} in the
trial function and then evaluating the integrals in the functional (4.1),
giving in this way an ordinary function of the variational parameters {c},
whichhas tobeminimized against the parameters. For a single parameter c
(Figure 4.2)
ε
(
c
)
c
min
c
0
ε
min
Figure 4.2
Plot of the variational energy near the minimum versus c
