6.20 Incremental Correlation Methods

6.20.3 Example

(June 30, 2021)

Example 6.47  iFCI n=2 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

View output