Example: Numerical Frequencies of an excited state: PH2¶
Example for an excited state geometry optimization and frequency calculation.
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). The ground state and excited state are open shell.
$ADFBIN/adf <<eor
TITLE PH2 Excited state geometry
atoms
P 0.000000 0.000000 0.0
H 0.7 0.0 0.7
H -0.7 0.0 0.7
end
XC
GGA BP86
END
UNRESTRICTED
CHARGE 0 1
BeckeGrid
Quality good
End
GEOMETRY
ITERATIONS 50
CONVERGENCE E=0.0001 grad=0.00001
END
SCF
converge 1.0e-9
END
basis
TYPE DZ
CORE NONE
end
excitations
LOWEST 10
onlysinglet
end
EXCITEDGO
STATE B2 1
OUTPUT=1
end
eor
mv TAPE21 PH2.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 1’. Accurate SCF convergence parameters are used.
$ADFBIN/adf <<eor
TITLE PH2 Excited state frequencies
atoms
P 0.000000 0.000000 0.002878
H 1.258230 0.000000 0.655775
H -1.258230 0.000000 0.655775
end
XC
GGA BP86
END
UNRESTRICTED
CHARGE 0 1
BeckeGrid
Quality good
End
GEOMETRY
FREQUENCIES
END
SCF
converge 1.0e-9
END
basis
TYPE DZ
CORE NONE
end
excitations
LOWEST 10
onlysinglet
end
EXCITEDGO
STATE A 1
OUTPUT=2
CPKS EPS=0.000001
end
eor