Abstract:
All-electron partitioning of wave functions into products ^core^vai of core and valence
parts in orbital space results in the loss of core-valence antisymmetry, uncorrelation of
motion of core and valence electrons, and core-valence overlap. These effects are studied
with the variational Monte Carlo method using appropriately designed wave functions
for the first-row atoms and positive ions.
It is shown that the loss of antisymmetry with respect to interchange of core and
valence electrons is a dominant effect which increases rapidly through the row, while the
effect of core-valence uncorrelation is generally smaller. Orthogonality of the core and
valence parts partially substitutes the exclusion principle and is absolutely necessary for
meaningful calculations with partitioned wave functions. Core-valence overlap may lead
to nonsensical values of the total energy.
It has been found that even relatively crude core-valence partitioned wave functions
generally can estimate ionization potentials with better accuracy than that of the traditional,
non-partitioned ones, provided that they achieve maximum separation (independence)
of core and valence shells accompanied by high internal flexibility of ^core
and Wvai- Our best core-valence partitioned wave function of that kind estimates the
IP's with an accuracy comparable to the most accurate theoretical determinations in the
literature.
