  Within the framework of non-relativistic quantum mechanics, the
ro-vibrational energy spectra of the improved deformed exponential-type
potential model are obtained using the Greene-Aldrich approximation scheme and
an appropriate coordinate transformation. With the help of the energy spectra,
analytical expressions of the vibrational partition function and other
thermodynamic functions are derived by employing the Poisson summation formula.
These thermodynamic functions are studied for the electronic states of hydrogen
dimer, carbon monoxide, nitrogen dimer and lithium hydride diatomic molecules,
as they vary with temperature and upper bound vibration quantum number.
