Dear Q-chem users and developers,

I want to calculate spin-flip TDDFT calculation on a combined system of C2 and C2H (having doublet spin symmetry in ground state) using Q-chem (5.4.0). I tried to do a restricted open-shell (ROKS) calculation on reference quartet state for further SF-DFT calculation. However, QChem showed the error “TDDFT based on ROKS is not available”.

Is there any other way I can do SF-TDDFT in Q-Chem starting from a ROKS reference calculation ? A part of the input file and the error message is attached herewith for your kind perusal.

Thanks in advance.

Regards,

Debroop

Input File:

$molecule

0 4

C -2.99885100 0.06836100 0.00006700

C -1.82163900 -0.02217400 -0.00007900

H -0.75857400 -0.10412700 -0.00009900

C 1.86005100 -0.19599300 0.00003500

C 3.08686700 0.16716100 -0.00000700

$end

$rem

JOBTYPE SP

SYMMETRY false

METHOD B3LYP

BASIS 6-31g**

CIS_N_ROOTS 6

!CIS_STATE_DERIV 1

SPIN_FLIP true

CIS_SINGLETS false

CIS_TRIPLETS false

unrestricted false

max_scf_cycles 200

MEM_TOTAL 200000

MEM_STATIC 2000

$end

Output File:

SCF time: CPU 29.02s wall 29.00s

<S^2> = 3.750000000

SCF energy in the final basis set = -152.5196979074

Total energy in the final basis set = -152.5196979074

Q-Chem fatal error occurred in module /home/debashree/Qchem5.3/qchem5.3/setman/setman_init.F, line 108:

TDDFT based on ROKS is not available