Dear Adf'ers,

                I'm doing some calculations on an organic ligand (30 atoms) for which
solvent (water) effects should be important.
                Geometry optimizations are ok, very cpu-time consuming though. When I run
frequency calculations on some conformations of the above ligand, including
solvent efects as well, one to three imaginary frequencies arise for all
the conformations studied. The imaginary frequencies range from 30 to 110
cm-1, that is they represent very floppy modes. I distorted one of the
above conformations (having one imaginary freq) following the imaginary
mode but I dind't succeed, a new imaginary freq arises.
                Now my question: normal, gas-phase, frequency calculations involving
numerical second derivatives are subjected to errors of +- 50 cm-1, aren't
they? Does the inclusion of the COSMO model affect the error bars for
frequencies? That is, is it safe to say that a 100 i cm-1 frequency is an
artifact when solvent effects are introduced variationally into the KS scf
equations?
                Thanks in advance.
                Regards,

                                                        Reinaldo
Received on 2001-06-29 12:51:13