If, however, a system contains more than 15-20 electrons the initial estimates of the orbitals have to be good enough to avoid divergences. Then, you have to choose the parameters of the hydrogenic orbitals carefully or perform the finite basis set calculations using the Gaussian94 to provide the initialization data for orbitals.
The dependence of the optimum value of the relaxation parameter
on the grid size is illustrated by the following table:
![]() |
![]() |
50 ![]() |
1.89 |
100 ![]() |
1.94 |
159 ![]() |
1.96 |
300 ![]() |
1.98 |
Now it is possible to set
to its near-optimal value by
using a semiempirical formula (B.Sobczak MSc Thesis, Torun 2002); see the
description of the
label above.
Optimum values of the orbital relaxation parameter are somewhat
smaller and are not directly related to the grid size. In most
cases choosing
should lead to
fairly good convergence rates.