How to get oscillator strength EOM-CCSD

How To
#1

Hello,

I want to compute excitation energies within EOM-CCSD method with the following input :

$rem
METHOD eom-ccsd
BASIS cc-pVDZ
ee_triplets 5
ee_singlets 5
calc_soc 1
CC_EOM_PROP true
solvent_method PCM
MEM_TOTAL 100000
MEM_STATIC 2000

$end

$pcm
theory                  CPCM
$end

$solvent
Dielectric              2.38
OpticalDielectric       1.9599999999999997
$end

$molecule
0 1

Which after the Davidson procedure has converged returns for the first singlet excited state :

 Excited state properties for  EOMEE-CCSD transition 1/A
 Dipole moment (a.u.): 0.152199 (X -0.073891, Y -0.115661, Z 0.065782)
 R-squared (a.u.): 1738.140327 (XX 855.376183, YY 825.213699, ZZ 57.550445)
 Gauge origin (a.u.): (0.000000, 0.000000, 0.000000)
 Angular momentum (a.u.) against gauge origin:
 (X 0.020760i, Y -0.032854i, Z -0.009493i)
 Traces of the OPDMs: Tr(AA) 44.000000, Tr(BB) 44.000000
 <S^2> = -0.000000

And thus my questions are where do I get the oscillator strength associated to this transition ? And what does OPDMs mean ?

Best regards,

Laure

#2

OPDM = one-particle density matrix.

The oscillator strengths should appear farther down in the output, e.g., using your input file for H2O molecule:

 EOMEE-CCSD calculation:   CPU 5.06 s  wall 3.24 s


 Start computing the transition properties

 ------------------------------------------------------------------------------
 The new SOC module will be executed
 Authors: Pavel Pokhilko and Evgeny Epifanovsky
 SOC 1e and mf integrals are evaluating by libqints...
 ------------------------------------------------------------------------------
 State A: ccsd: 0/A
 State B: eomee_ccsd/rhfref/singlets: 1/A
 Energy GAP = 0.314615 a.u. = 8.561106 eV
 Transition dipole moment (a.u.):
   A->B: 0.369590 (X 0.000000, Y -0.369590, Z 0.000000)
   B->A: 0.376400 (X 0.000000, Y -0.376400, Z 0.000000)
 Oscillator strength (a.u.): 0.029178
 Transition angular momentum against gauge origin (a.u.):
   A->B:  (X -0.115529i, Y 0.000000i, Z 0.149221i)
   B->A:  (X 0.118861i, Y 0.000000i, Z -0.153525i)
 Norm of one-particle transition density matrix:
   A->B: 0.957596;   B->A: 0.970619
   ||gamma^AB||*||gamma^BA||: 0.929461
#3

To compute transition properties (such as oscillator strength), you need to add this to the input: CC_TRANS_PROP = 1

#4

Hello, I want to calculate the resonant auger decay using the EOM-CCSD. The output calculated according to the cvs-ee-states and ip-states instructions used in the Q-chem manual belongs only to the resonant participator decay. How to configure it to calculate the resonance spectator decay? thanks.

#5

In the case of resonant Auger decay, we distinguish between participator and spectator/observer decay. The decay channels for participator decay are 1h states and decay channels for spectator decay are 2h1p states. Both 1h and 2h1p states can be computed by EOM-IP-CCSD, however, the energies of the latter states will be overestimated. The two types of states can be distinguished by analyzing EOM-IP amplitudes: the states with R1^2 close to 1 correspond to participator decay whereas those with R2^2 close to 1 correspond to spectator decay.

Here’s a sample of the rem section of the input for the benzene molecule (for the opitmized structure see J. Chem. Phys., 158, 064109, (2023)):

$rem
jobtype = sp
method = eom-ccsd
ip_states [4,0,0,0,0,0,0,0]
cvs_ee_states [0,0,0,0,0,0,1,0]
basis = gen
CC_DO_DYSON 1
CC_DO_FESHBACH 1
mem_total = 100000
$end

In the output you will find the first three EOM-IP states with R1^2 close to 1 (participator decay) and the fourth EOM-IP state with R2^2 is close to 1 (spectator/observer decay)

image
image1104×1576 143 KB

#6

Ok, thank you very much for your answer!