Example: Analytic Frequencies: CN¶
Calculation of analytical second derivatives is requested by specifying
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.