Jaguar Vibrational Frequencies

Vibrational frequencies are calculated by Jaguar using analytic second derivatives by default for restricted and unrestricted HF and DFT wave functions in the gas phase and in solution, for basis sets that do not include f functions. (See Basis Sets for more information on basis sets.) All other frequency calculations are done with numerical derivatives of analytically computed forces. Frequencies can be calculated numerically for HF, LMP2, and DFT wave functions in gas phase or in solution. Frequencies are always calculated numerically for RODFT wave functions when an effective core potential is used. (Note that RODFT frequencies are calculated with an unrestricted formalism, as the restriction is applied only in orbital generation.)

Analytic frequency calculations are much faster than numerical frequency calculations. When frequencies are calculated analytically, molecular symmetry is turned off for the frequency calculation itself, but is used for the rest of the job. To calculate frequencies numerically, set nmder=2 in the gen section of the input file, as described in The gen Section of the Jaguar Input File.

In addition to generating a file containing frequency information, the output Maestro file contains the lowest two frequencies, the highest frequency, and the number of negative frequencies as properties. The lowest frequencies and the number of negative frequencies can be used to check whether a stationary point is a saddle point.