# 7.11.9 Examples

Example 7.110  Input for a RAS-2SF-CI calculation of three states of the DDMX tetraradical using RASCI1. The active space (RAS2) contains $4$ electrons in the $4$ singly occupied orbitals in the ROHF quintet reference. Natural orbital occupancies are requested.

$molecule 0 5 C 0.000000 0.000000 1.092150 C -1.222482 0.000000 0.303960 C -2.390248 0.000000 1.015958 H -2.344570 0.000000 2.095067 H -3.363161 0.000000 0.537932 C -1.215393 0.000000 -1.155471 H -2.150471 0.000000 -1.702536 C 0.000000 0.000000 -1.769131 C 1.215393 0.000000 -1.155471 H 2.150471 0.000000 -1.702536 C 1.222482 0.000000 0.303960 C 2.390248 0.000000 1.015958 H 2.344570 0.000000 2.095067 H 3.363161 0.000000 0.537932$end

$rem EXCHANGE hf CORRELATION rasci BASIS 6-31g UNRESTRICTED false MEM_TOTAL 4000 MEM_STATIC 100 RAS_ROOTS 3 RAS_ACT 4 RAS_ELEC 4 RAS_OCC 25 RAS_SPIN_MULT 0 RAS_NATORB true$end


Example 7.111  Input for a RAS-2IP-CI calculation of triplet states of F${}_{2}$ molecule using the dianion closed shell F${}_{2}^{2-}$ as the reference determinant. RASCI1 code is used

$molecule -2 1 F F 1 1.4136$end

$rem EXCHANGE hf CORRELATION rasci BASIS cc-pVTZ MEM_TOTAL 4000 MEM_STATIC 100 RAS_ROOTS 2 RAS_ACT 6 RAS_ELEC 10 RAS_OCC 4 RAS_SPIN_MULT 3$end


Example 7.112  Input for a FCI/STO-3G calculation of water molecule expanding the RAS2 space to the entire molecular orbital set. RASCI code is used.

$molecule 0 1 O 0.000 0.000 0.120 H -0.762 0.000 -0.479 H 0.762 0.000 -0.479$end

$rem EXCHANGE hf CORRELATION rasci BASIS sto-3g MEM_TOTAL 4000 MEM_STATIC 100 RAS_ROOTS 1 RAS_ACT 7 RAS_ELEC 10 RAS_OCC 0 RAS_SPIN_MULT 1 RAS_DO_HOLE false RAS_DO_PART false$end


Example 7.113  Methylene single spin-flip calculation using RASCI2

$molecule 0 3 C 0.0000000 0.0000000 0.0000000 H -0.8611113 0.0000000 0.6986839 H 0.8611113 0.0000000 0.6986839$end

$rem EXCHANGE HF CORRELATION RASCI2 BASIS cc-pVDZ AUX_BASIS rimp2-cc-pVDZ UNRESTRICTED false RAS_ACT_OCC 1 ! # alpha electrons RAS_ACT_VIR 1 ! # virtuals in active space RAS_ACT_DIFF 0 ! # set to 1 for odd # of e-s RAS_N_ROOTS 4 SET_ITER 25 ! number of iterations in RASCI$end


Example 7.114  Two methylene separated by 10 Å; double spin-flip calculation using RASCI2. Note that the $\langle S^{2}\rangle$ values for this case will not be uniquely defined at the triply-degenerate ground state.

$molecule 0 5 C 0.0000000 0.0000000 0.0000000 H -0.8611113 0.0000000 0.6986839 H 0.8611113 0.0000000 0.6986839 C 0.0000000 10.0000000 0.0000000 H -0.8611113 10.0000000 0.6986839 H 0.8611113 10.0000000 0.6986839$end

$rem EXCHANGE HF CORRELATION RASCI2 BASIS cc-pVDZ AUX_BASIS rimp2-cc-pVDZ RAS_ACT_OCC 2 ! # alpha electrons RAS_ACT_VIR 2 ! # virtuals in active space RAS_ACT_DIFF 0 ! # set to 1 for odd # of e-s UNRESTRICTED false RAS_N_ROOTS 8 SET_ITER 25$end


Example 7.115  RASCI2 calculation of the nitrogen cation using double spin-flip.

$molecule 1 6 N N 1 4.5$end

$rem EXCHANGE HF CORRELATION RASCI2 BASIS 6-31G* AUX_BASIS rimp2-VDZ RAS_ACT_OCC 3 ! # alpha electrons RAS_ACT_VIR 3 ! # virtuals in active space RAS_ACT_DIFF 1 ! # for odd # e-s, cation UNRESTRICTED false N_FROZEN_CORE 2 N_FROZEN_VIRTUAL 2 RAS_N_ROOTS 8 SET_ITER 25$end


Example 7.116  RAS(h,p)-1SF calculation of the nitrogen cation using LibRASSF.

$molecule 0 7 N N 1 1.75$end

$rem EXCHANGE HF CORRELATION RASCI2 BASIS cc-pvdz LIBRASSF 1 RASSF_DELTA_ALPHA 1 RASSF_DELTA_BETA 1 RAS_N_ROOTS 4 RAS_DO_HOLE 1 RAS_DO_PART 1 RAS_NATORB 0$end