EOM-CC(2,3) is invoked by METHOD=EOM-CC(2,3). The following options are available:
EOM_PRECONV_SD
EOM_PRECONV_SD
Solves the EOM-CCSD equations, prints energies, then uses EOM-CCSD vectors
as initial vectors in EOM-CC(2,3). Very convenient for calculations using energy additivity schemes.
TYPE:
INTEGER
DEFAULT:
0
OPTIONS:
Do SD iterations
RECOMMENDATION:
Turning this option on is recommended
CC_REST_AMPL
CC_REST_AMPL
Forces the integrals, , and amplitudes to be determined in the full
space even though the CC_REST_OCC and CC_REST_VIR
keywords are used.
TYPE:
LOGICAL
DEFAULT:
TRUE
OPTIONS:
FALSE
Do apply restrictions
TRUE
Do not apply restrictions
RECOMMENDATION:
None
CC_REST_TRIPLES
CC_REST_TRIPLES
Restricts amplitudes to the active space, i.e., one electron should be
removed from the active occupied orbital and one electron should be added to
the active virtual orbital.
TYPE:
INTEGER
DEFAULT:
1
OPTIONS:
1
Applies the restrictions
RECOMMENDATION:
None
CC_REST_OCC
CC_REST_OCC
Sets the number of restricted occupied orbitals including frozen occupied
orbitals.
TYPE:
INTEGER
DEFAULT:
0
OPTIONS:
Restrict occupied orbitals.
RECOMMENDATION:
None
CC_REST_VIR
CC_REST_VIR
Sets the number of restricted virtual orbitals including frozen virtual
orbitals.
TYPE:
INTEGER
DEFAULT:
0
OPTIONS:
Restrict virtual orbitals.
RECOMMENDATION:
None
To select the active space, orbitals can be reordered by specifying the new order in the $reorder_mosection. The section consists of two rows of numbers ( and sets), starting from , and ending with , where is the number of the last orbital specified.
The following example $reorder_mo section shows orbitals 16 and 17 swapped for both and electrons:
$reorder_mo 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 17 16 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 17 16 $end
Example 7.104 EOM-SF(2,3) calculations of methylene.
$molecule 0 3 C H 1 CH H 1 CH 2 HCH CH = 1.07 HCH = 111.0 $end $rem METHOD eom-cc(2,3) BASIS 6-31G SF_STATES [2,0,0,2] N_FROZEN_CORE 1 N_FROZEN_VIRTUAL 1 EOM_PRECONV_SD 20 Get EOM-CCSD energies first (max_iter=20). $end
Example 7.105 This is active-space EOM-SF(2,3) calculations for methane with an elongated CC bond. HF MOs should be reordered as specified in the $reorder_mosection such that active space for triples consists of sigma and sigma* orbitals.
$molecule 0 3 C H 1 CH H 1 CHX 2 HCH H 1 CH 2 HCH 3 A120 H 1 CH 2 HCH 4 A120 CH = 1.086 HCH = 109.4712206 A120 = 120. CHX = 1.8 $end $rem METHOD eom-cc(2,3) BASIS 6-31G* SF_STATES [1,0] N_FROZEN_CORE 1 EOM_PRECONV_SD 20 does eom-ccsd first, max_iter=20 CC_REST_TRIPLES 1 triples are restricted to the active space only CC_REST_AMPL 0 ccsd and eom singles and doubles are full-space CC_REST_OCC 4 specifies active space CC_REST_VIR 17 specifies active space PRINT_ORBITALS 10 (number of virtuals to print) $end $reorder_mo 1 2 5 4 3 1 2 3 4 5 $end
Example 7.106 EOM-IP-CC(2,3) calculation of three lowest electronic states of water cation.
$molecule 0 1 H 0.774767 0.000000 0.458565 O 0.000000 0.000000 -0.114641 H -0.774767 0.000000 0.458565 $end $rem METHOD eom-cc(2,3) BASIS 6-311G IP_STATES [1,0,1,1] $end