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Stability analysis of spinrestricted closedshell ground states is
enabled by
 $scfinstab singlet

for singlet instabilities,
 $scfinstab triplet

for triplet instabilities (most common), and
 $scfinstab nonreal

for nonreal instabilities.
After that, it is necessary to specify the IRREPs of the electronic
Hessian eigenvectors (``orbital rotations'') to be considered. Without
additional knowledge of the system one usually needs to calculate the
lowest eigenvalue within every IRREP:
$soes all 1
Positivity of the lowest eigenvalues in all IRREPs is sufficient for
stability of the ground state solution. If one is interested in, say,
the lowest eigenvalues in IRREPs eg
and t2g
only, one
may specify:
$soes
eg 1
t2g 1
Triplet instabilities in the totally symmetric IRREP indicate
open shell diradical states (singlet or triplet). In this case, start
MOs for spinsymmetry broken UHF or UKS ground state calculation can
be generated by specifying
$start vector generation
escf will provide the start MOs (
$uhfmo_alpha,
$uhfmo_beta) as well as occupation numbers (
$alpha shells, $beta shells) for a spinunrestricted
calculation with equal numbers of and
electrons (pseudosinglet occupation).
Next: Vertical Excitation and CD
Up: How to Perform
Previous: Polarizabilities and Optical Rotations
Contents
Index
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