Gergely Szász and Attila Kovács

Investigation of the DFT-Derived Scaled Quantum Mechanical Method for Cage-Like Systems.

The Vibrational Analysis of Adamantane.

Molecular Physics, 96 (1999) 161-167.



The Becke3-Lee-Yang-Parr(B3-LYP)/6-31G* derived scaled quantum mechanical (SQM) method developed recently by Pulay et al. has been investigated for cage-like systems using adamantane as model molecule. The scale factors of Pulay et al. were found to be well transferable to adamantane except the general heavy atom scale factor for the CC stretching modes of the skeleton. For these vibrations a new individual scale factor was developed in the present study. A complete vibrational analysis of adamantane and adamantane-d16 has been performed. The experimental vibrational spectra of the compounds were reinterpreted using the scaled B3-LYP/6-31G* harmonic force field. Some assignments of earlier less sophisticated investigations were revised and reliable predictions for the IR and Raman inactive fundamentals were proposed.