25.2.2 Frozen-core orbitals

CORE, $n_1,n_2,\ldots,n_8$;

$n_i$ is the number of frozen-core orbitals in irrep number $i$. These orbitals are doubly occupied in all configurations, i.e., not correlated. If no CORE card is given, the program uses the same core orbitals as the last CI calculation; if there was none, then the atomic inner shells are taken as core. To avoid this behaviour and correlate all electrons, specify

CORE