NACs for highly excited states with EOM-CCSD

Questions
#1

Hello,

I want to calculate the NACs between inner valence excited states of a water dimer. In particular I focus on the states with excitation from orbital 4.
I thought of using EOM-CCSD. As the CVS-EOM-CCSD couplings are not implemented I thought of doing a normal SCF and then reorder the MOs such as that orbital number 4 goes in place of the HOMO (number 10) and then freeze all orbitals below.

However from the results it doesn’t seem working the reordering of the MOs.
How can this be done?

Here’s my input:

$molecule
0 1
O 1.3832027274 0.0005305073 -0.1113010031
H 1.7431113123 0.7547042488 0.3616213140
H 1.7415847054 -0.7598653852 0.3527901748
O -1.5136862649 -0.0010516718 0.1210592194
H -1.8809444243 0.0041975492 -0.7638747932
H -0.5598832934 0.0051329031 -0.0286024265
$end

$rem
SYMMETRY = false
EXCHANGE = HF
CORRELATION = CCSD
BASIS = sto-3g
MAX_CIS_CYCLES = 100
$end

@@@
$molecule
0 1
O 1.3832027274 0.0005305073 -0.1113010031
H 1.7431113123 0.7547042488 0.3616213140
H 1.7415847054 -0.7598653852 0.3527901748
O -1.5136862649 -0.0010516718 0.1210592194
H -1.8809444243 0.0041975492 -0.7638747932
H -0.5598832934 0.0051329031 -0.0286024265
$end

$rem
EXCHANGE = HF
CORRELATION = ccsd
BASIS = sto-3g
EE_SINGLETS = [10]
GUI = 2
CALC_NAC = 2
N_FROZEN_CORE = 9
SCF_GUESS = read
MOM_START = 1
$end

$occupied
1 2 3 5 6 7 8 9 10 4
1 2 3 5 6 7 8 9 10 4
$end

Thank you very much in advance

#2

You should be using $reorder_mo instead of $occupied. Do an SCF calculation with “GEN_SCFMAN = false” and $reorder_mo section, and then read the SCF solution with “MAX_SCF_CYCLES = 0” in the EOM-CC calculation with all but one orbital in the occupied valence space. Not sure if the results will be reliable with such a super-truncated occupied space, but that is for you to figure out.

$molecule
0 1
O 1.3832027274 0.0005305073 -0.1113010031
H 1.7431113123 0.7547042488 0.3616213140
H 1.7415847054 -0.7598653852 0.3527901748
O -1.5136862649 -0.0010516718 0.1210592194
H -1.8809444243 0.0041975492 -0.7638747932
H -0.5598832934 0.0051329031 -0.0286024265
$end
$rem
SYMMETRY = false
EXCHANGE = HF
BASIS = sto-3g
MAX_CIS_CYCLES = 100
GEN_SCFMAN = false
$end
$reorder_mo
1 2 3 5 6 7 8 9 10 4 11
1 2 3 5 6 7 8 9 10 4 11
$end
@@@
$molecule
read
$end
$rem
EXCHANGE = HF
CORRELATION = ccsd
BASIS = sto-3g
EE_SINGLETS = [10]
CALC_NAC = 2
N_FROZEN_CORE = 9
SCF_GUESS = read
MAX_SCF_CYCLES = 0
$end

#3

Dear kaushik,

thank you for the answer. It works well and the energies are reasonable.

I have another question. This way I compute the NACs between ground state and each excited state. Is there a way to compute the coupling between 2 excited states?

Thank you in advance

#4

You may set the CC_STATE_TO_OPT REM or set “CC_TRANS_PROP = 2” and check if they work for NACs between EOM-CC target states in CCMAN2. If not, let us know.