Example 6.6.47 iFCI calculation for triplet ethylene. PP triplet is used as reference.
$molecule 0 1 C 0.0000000000 0.0000000000 0.0020303630 C 0.0000000000 0.0000000000 1.3369696370 H 0.9228964204 0.0000000000 -0.5679991115 H -0.9228964204 0.0000000000 -0.5679991115 H 0.9228964204 0.0000000000 1.9069991115 H -0.9228964204 0.0000000000 1.9069991115 $end $rem METHOD hf BASIS 6-31G* SCF_ALGORITHM rca_diis SYMMETRY off SYM_IGNORE true $end @@@@ $molecule 0 3 read $end $rem EXCHANGE HF CORRELATION CCVB CCVB_METHOD 4 GVB_RESTART 0 GVB_ORB_CONV 6 BASIS 6-31G* UNRESTRICTED false SCF_GUESS read SYMMETRY off SYM_IGNORE true $end @@@@ $molecule 0 1 read $end $rem EXCHANGE HF CORRELATION IFCI BASIS 6-31G* AUX_BASIS RIMP2-VDZ IFCI_TUPLES 2 IFCI_READ 0 IFCI_TRIPLETS 1 IFCI_ZETA 55 HBCI_EPS1 1000 IFCI_REF_ITER 0 $end