NHDT: Vibrational Circular Dichroism

Sample directory: adf/VCD_COG_NHDT/

Analytical frequencies with subsequent calculation of vibrational circular dichroism (VCD)

The VCD keyword (available since ADF2007.01) can be used to calculate VCD spectra. It is important to note that the VCD keyword only works in combination with the keys AnalyticalFreq and symmetry NOSYM.

Recomended is use to use high accuracy for the geometry optimization which one needs to do before the frequency calculation. This simple example is an NHDT molecule, which is NH₃ where one hydrogen atom is replaced with deuterium and another with tritium.

First the atoms are created, next the molecule is calculated.

$ADFBIN/adf -n1 <<eor
create H q=1 m=2.014101778 file=$ADFRESOURCES/TZP/H
XC
 gga Becke Perdew
end
end input
eor
mv TAPE21 t21.D

$ADFBIN/adf -n1 <<eor
create H q=1 m=3.01604927 file=$ADFRESOURCES/TZP/H
XC
 gga Becke Perdew
end
end input
eor
mv TAPE21 t21.T

$ADFBIN/adf -n1 <<eor
create N file=$ADFRESOURCES/TZP/N
XC
 gga Becke Perdew
end
end input
eor
mv TAPE21 t21.H

$ADFBIN/adf -n1 <<eor
create N file=$ADFRESOURCES/TZP/N
XC
 gga Becke Perdew
end
end input
eor
mv TAPE21 t21.N

Next the molecule is calculated.

$ADFBIN/adf <<eor
Title Single Point calc.

Atoms
    N         0.000000    0.000000    0.010272
    H        -0.471582   -0.816803    0.407861
    H.D       0.943163    0.000000    0.407861
    H.T      -0.471582    0.816803    0.407861
End

Symmetry NOSYM

xc
 GGA BP86
end

Fragments
N     t21.N
H     t21.H
H.D   t21.D
H.T   t21.T 
End

AnalyticalFreq
End

VCD

end input
eor