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One body term
Another important term of our trialfunction it is the onebody term.
In fact as pointed out in Ref. (36), it is easier to optimize a onebody term explicitly
rather than including more orbitals in the determinantal basis set.
Moreover, even if it is possible to satisfy nuclear cusp conditions (see Appendix C) with the pairing determinant, this has to be done iteratively during the optimization process adding constraints to the variational parameters or approximately
disregarding the term of the eq.1.22. In order to solve efficiently this problem we included nuclear cusp conditions explicitly in the onebody term, in the same way of ref. (37):

(1.23) 
where
orbital is used to satisfy the nuclear cusp conditions on nucleus
:

(1.24) 
and the
is a linear combination of atomic orbitals centered on the nucleus
, and that do not effect the nuclear cusp condition.
We have used Gaussian and exponential orbitals
such to have a smooth behaviour
close to the corresponding nuclei, namely as:

(1.25) 
or with larger power,
in order to preserve the nuclear cusp conditions (1.24).
The basis set
is the same used in the socalled threebody term that we are going to describe in the following. The same kind of behavior has been imposed for the orbitals appearing in the determinant. In this way the nuclear cusp conditions are very easily satisfied for a general system containing many atoms, in a simple and efficient way.
Next: Two body Jastrow term
Up: Functional form of the
Previous: Pairing determinant
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Claudio Attaccalite
20051107