METHODOLOGICAL STUDY OF BECKE3-LYP DENSITY-FUNCTIONAL ADAPTED TO THE DETERMINATION OF ACCURATE INFRARED SIGNATURE FOR HYDROGEN-BONDED COMPLEXES

The density functional theory is able to accurately reproduce the expe rimentally observed infrared shifts for donor or acceptor molecules in volved in hydrogen-bonded complexes, For this purpose it is shown that it is necessary to change the Becke parametrization of the exchange c orrelation energy in the Becke3-LYP density functional. This proposal has been applied to the weak (FH)(2) and to the medium strength FH...N H3 hydrogen-bonded complexes. With the new proposed parametrization of the Becke functional it is shown that it is not possible to concomita ntly represent intermolecular properties and binding energies with goo d accuracy because the dispersion energy is not included in DFT. (C) 1 997 Elsevier Science B.V.