24.2 Quadratic configuration interaction, QCI

QCI or QCISD performs quadratic configuration interaction, QCISD. Using the QCI(T) or QCISD(T) commands, the contributions of connected triples are also computed by perturbation theory. Normally, no further input is needed if the QCI card follows the corresponding HF-SCF. Otherwise, occupancies and orbitals can be specified as in the CI program. For modifying DIIS directives, see section 24.5. For first-order QCISD and QCIDF(T) properties see section .

For avoiding error exits in case of no convergence, see CCSD(T).