TaFn and TaCln atomization energies for n=1-5

TaFn and TaCln atomization energies are computed for n = 1-5. The geometrie s, frequencies, and atomization energies are determined using density funct ional theory. Both the BP86 and B3LYP functionals are used. Our best atomiz ation energies are obtained by scaling the DFT results on the basis of the experimental TaX5 atomization energies and including a correction for spin- orbit effects. For TaFn, our corrected values are in good agreement with ex periment. For TaF, TaCl, and TaCl2 the atomization energies are also comput ed at the coupled cluster level of theory in conjunction with relativistic effective core potentials. The CCSD(T) complete basis set (CBS) limit is ob tained by extrapolation. The scaled DFT values are in good agreement with t hese CCSD(T) CBS values. The TaF, results and the calibration calculations suggest that the scaled TaCln DFT atomization energies are accurate to 3-5 kcal/mol.