L. Joubert et al., ADVANTAGES AND DRAWBACKS OF THE QUANTUM-CHEMISTRY METHODOLOGY IN PREDICTING THE THERMOCHEMICAL DATA OF LANTHANIDE TRIHALIDE MOLECULES, Journal of alloys and compounds, 277, 1998, pp. 934-939
DFT calculations have been carried out on six lanthanide trihalide mol
ecules, using Stuttgart ECPs on the lanthanides and a 6-31G all-elect
rons basis set on the halogens. These calculations have been compared
to previous theoretical and experimental data. Calculated bond lengths
and vibrational frequencies are found to be in good agreement with pr
evious theoretical results. The variations observed between experiment
al and theoretical results are discussed. Therefore, thermochemical da
ta have been derived from such calculations. In this paper, the advant
ages and drawbacks of this methodology are discussed in the framework
of the selected heavy elements. The different factors which influence
the estimated thermochemical data have been compared. While molecular
parameters seem to have a weak influence on the thermochemical functio
ns, low frequencies (flat energy surfaces along the out-of-plane disto
rtion) and the electronic partition function have been revealed to be
the main factors for the accuracy of the predicted thermochemical data
. (C) 1998 Elsevier Science S.A.