## Name

AVEPMO — Averaged density matrix in MO basis for the first `n`

eigenstates.

## Description

During a CI calculation, AVEPMO computes the averaged density matrix in the molecular orbital basis corresponding
to the first `n`

states and the averaged natural occupancies for the CI-active natural
MOs are printed. [Natural orbitals come from the fact that in CI, the density matrix is no longer diagonal in the MO basis.
The diagonalization of this density matrix gives natural MOs as eigenvectors and natural occupancies as eigenvalues.
Natural orbitals are best (in a least squares sense) to converge a CI expansion.]
From this, it suggests the best parameters `x,y,z,r`

(in a least squares fit sense) for
SCFCI(`x,y,z,r`

). The fit is delivered for
an average of the one, one+two, ...., one+two+...+`n`

first electronic eigenstates. The idea
is to prepare by an oriented SCFCI the best MOs to describe the entire set of the first eigenstates.

The user should note that if `n`

exceeds the number of CI eigenstates
(`m`

) included in the calcuation, then information printed will be restricted to just the
`m`

available eigenstates (rather than all `n`

). To avoid this,
use CISTATE=`m`

, where
`m ≥ n`

.