Example: Spin-flip excited state geometry optimization: CH2

Download EGO_CH2_sf.run

Example for a spin-flip excited state geometry optimization with a triplet reference, and a frequency calculation afterwards.

Needed for such excited state optimizations are the key EXCITATIONS (to calculate excitation energies), the key GEOMETRY (to do a geometry optimization) and the key EXCITEDGO (to select for which excitation a geometry optimization should be performed). In this case spin-flip excitations are calculated.

$ADFBIN/adf <<eor
TITLE CH2 Excited state geometry with triplet reference and spin-flip excitation
atoms
    C          0.000000    0.000000   0.0
    H          0.7         0.0        0.7
    H         -0.7         0.0        0.7
end
UNRESTRICTED
CHARGE 0 2
GEOMETRY
 ITERATIONS 50
 CONVERGENCE E=0.0001 grad=0.0001
END
basis
 TYPE DZP
CORE NONE
end
excitations
LOWEST 10
end
TDA
SFTDDFT
FORCEALDA
EXCITEDGO
 STATE  B2 1
 OUTPUT=2
end
SYMMETRY C(2V)
eor
mv TAPE21 CH2.t21

Next the frequencies are calculated of the excited state. A restart is used to pick up the excited state geometry of the previous calculation. Note that in a numerical FREQUENCIES calculation symmetry is turned off except to reduce the number of points calculated. Thus irrespective of the specified point group symmetry the symmetry label A of SYMMETRY NOSYM should be used to select the excited state. Care should be taken to ensure that the correct state is chosen in this frequencies calculation as the excited state number can change when the point group is changed. In this case instead of ‘B2 1’ one needs to select ‘A 2’.

$ADFBIN/adf <<eor
TITLE CH2 Excited state frequencies with triplet reference and spin-flip excitation
atoms
    C          0.000000    0.000000   0.0
    H          0.7         0.0        0.7
    H         -0.7         0.0        0.7
end
RESTART CH2.t21
UNRESTRICTED
CHARGE 0 2
GEOMETRY
 FREQUENCIES
END
basis
 TYPE DZP
CORE NONE
end
excitations
LOWEST 10
end
TDA
SFTDDFT
FORCEALDA
EXCITEDGO
 STATE  A 2
 OUTPUT=2
end
SYMMETRY C(2V)
eor