Example: Analytic Frequencies: CN¶
Calculation of analytical second derivatives is requested by specifying
AnalyticalFreq
End
in the ADF input.
A good quality is specified for the numerical Becke integration to be sure of reliable results. In general, it seems advisable to use high accuracy for heavy nuclei at the moment, whereas default integration accuracy is usually sufficient for light atoms. The precision of the fit may be improved with the ZlmFit block keyword.
$ADFBIN/adf << eor
title CN
atoms
N -1.3 0.0 0.0
C 0.0 0.0 0.0
end
Basis
Type DZ
Core None
End
charge -1
XC
LDA Xonly
End
BeckeGrid
quality good
End
AnalyticalFreq
End
End input
eor
After SCF is completed, the energy second derivatives matrix is calculated and analysed, which yields in this case one frequency.