First principles study of the partition function and heat capacity of OH
− anion is conducted at high temperatures (2000K-10,000K). Firstly, with
the quantum chemical ab inito methods (RASSCF with CASPT2 correction)
were used to cal- culate potential energy curves of the ground and
excited electronic states; the energy points were fitted to analytical
representation of the curves. Secondly, the statistical thermodynamics
calculations with the classical method with the quantum Wigner-Kirkwood
correction were performed to obtain partition func- tion and heat
capacity. Thermochemical tables and datasets usually give quantities up
to 6000K (sometimes even more) and often are not reliable at the highest
temperatures, it is shown that in particular electronic excited states
could be missing. Parti- tion function is compared with the only
available Barklem and Collet dataset. Discrepancies between heat
capacity data (given in NIST-JANAF and Burcat databases) are pointed out
- the inclusion of excited electronic states is crucial.
First-principles study of the phonon spectrum and heat capacity of TATB crystal
