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12. Excited State Dynamics

  • We will follow Orca 5.0.4 Manual, "Section 8.15: Excited State Dynamics", pages 394-414.
  • Also see "Section 9.38: Simulation and Fit of Vibronic Structure in Electronic Spectra, Resonance Raman Excitation Profiles and Spectra with the ORCA_ASA Program"
  • Also see "Section 9.39 More on the Excited State Dynamics module" for full list of keywords for ORCA_ESD

12.1 Absorption spectrum of Benzene using the ideal model, Adiabatic Hessian (AH)

  • Let's predict the absorption spectrum of benzene, which has one band above 220 nm correponding to a symmetry forbidden excitation to the S1 state.

12.1.1 S0 state OPT and FREQ

!wB97X-D3 RIJCOSX DEF2-SVP  DEF2/J TIGHTSCF TIGHTOPT FREQ XYZFILE

%BASE "s0"

*XYZFILE 0 1 geom_UFF.xyz

%MAXCORE 64000

%SCF
  MAXITER 150
END

%PAL
  NPROCS 16
END

%GEOM
  CALC_HESS TRUE
  RECALC_HESS 5
  MAXITER 50
END
  • geom_UFF.xyz
12
benzene
C        1.38212000       -0.21688000        0.00497000
C        0.50328000       -1.30535000       -0.00923000
C       -0.87883000       -1.08847000       -0.01427000
C       -1.38212000        0.21688000       -0.00497000
C       -0.50328000        1.30535000        0.00930000
C        0.87883000        1.08847000        0.01420000
H        2.45137000       -0.38467000        0.00882000
H        0.89264000       -2.31521000       -0.01633000
H       -1.55873000       -1.93054000       -0.02535000
H       -2.45137000        0.38467000       -0.00882000
H       -0.89264000        2.31520000        0.01653000
H        1.55873000        1.93054000        0.02515000

12.1.2 S1 state OPT and FREQ

!wB97X-D3 RIJCOSX DEF2-SVP  DEF2/J TIGHTSCF TIGHTOPT FREQ XYZFILE

%BASE "s1"

*XYZFILE 0 1 s0.xyz

%MAXCORE 64000

%SCF
  MAXITER 150
END

%PAL
  NPROCS 16
END

%GEOM
  CALC_HESS   TRUE
  RECALC_HESS 5
  MAXITER     50
END

%TDDFT
 NROOTS       5
 IROOT        1
 TDA          FALSE
 TRIPLETS     FALSE
END

12.2 ESD (ABS)

  • Since the first transition of benzene is symmetry forbidden with a tiny oscillator strength ($\thickapprox 10^{-6}$ or less) and thus all the intensity comes from vibronic coupling (HT effect). So, we have to set DOHT TRUE in the ESD calculation. In molecules with strongly allowed transitions that usually can be left as FALSE (the default).
!wB97X-D3 RIJCOSX DEF2-SVP  DEF2/J TIGHTSCF ESD(ABS) XYZFILE

%BASE "esd"

*XYZFILE 0 1 s0.xyz

%MAXCORE 64000

%SCF
  MAXITER 150
END

%PAL
  NPROCS 16
END

%TDDFT
 NROOTS       5
 IROOT        1
 TDA          FALSE
 TRIPLETS     FALSE
END

%ESD GSHESSIAN "s0.hess"
  ESHESSIAN    "s1.hess"
  DOHT TRUE
END

12.3 ESD (FLUOR)

!wB97X-D3 RIJCOSX DEF2-SVP  DEF2/J TIGHTSCF ESD(FLUOR) XYZFILE

%BASE "esd_flu"

*XYZFILE 0 1 s0.xyz

%MAXCORE 64000

%SCF
  MAXITER 150
END

%PAL
  NPROCS 16
END

%TDDFT
 NROOTS       5
 IROOT        1
 TDA          FALSE
 TRIPLETS     FALSE
END

%ESD GSHESSIAN "s0.hess"
  ESHESSIAN    "s1.hess"
  DOHT TRUE
  LINES           VOIGT
  LINEW           75
  INLINEW         200
END
  • NOTE: For plotting absorption and emission spectrum together, one has to normalize both the plots as done in https://doi.org/10.1063/1.5010895.
  • Fluoroescence rate constant is printed in the output
          ***Everything is set, now computing the correlation function***

Homogeneous linewidth is:                       75.00 cm-1
Inhomogeneous linewidth is:                     200.00 cm-1
Number of points:                               65536
Maximum time:                                   1061.77 fs
Spectral resolution:                            5.00 cm-1
Temperature used:                               298.15 K
Z value:                                        1.703696e-44
Cutoff for the correlation function:            1.00e-06
Adiabatic energy difference:                    44188.52 cm-1
0-0 energy difference:                          43045.64 cm-1
Reference transition dipole (x,y,z):            (-0.00420 0.00000),
                                                (0.00290 0.00000),
                                                (0.00001 0.00000) 
Calculating correlation function:               ...done
Last element of the correlation function:       0.000000,0.000000
Computing the Fourier Transform:                ...done

The calculated fluorescence rate constant is    2.043006e+07 s-1          <----- HERE
with 0.02% from FC and 99.98% from HT

The fluorescence spectrum was saved in          esd_flu.spectrum

Total run time: 0 hours 6 minutes 49 seconds

12.4 TCUTFREQ

  • Sometimes, low frequencies have displacements that are just too large, or the experimental modes are too anharmonic and you might want to remove them. It is possible to do that setting the TCUTFREQ flag (in cm−1), and all frequencies below the given threshold will be removed.

12.5 ESD (ABS) with STEOM-DLPNO-CCSD

  • Do single point DLPNO using APPROXADEN TRUE and DFT-level geometry and hessian
!STEOM-DLPNO-CCSD RIJCOSX DEF2-SVP  DEF2-SVP/C TIGHTSCF ESD(ABS) XYZFILE

%BASE "esd"

*XYZFILE 0 1 s0.xyz

%MAXCORE 5000

%SCF
  MAXITER 150
END

%PAL
  NPROCS 24
END

%MDCI
 NROOTS       5
 MAXITER      100
END

%ESD GSHESSIAN "s0.hess"
  ESHESSIAN    "s1.hess"
  DOHT TRUE
  APPROXADEN TRUE
END