In this study, the improved Tietz potential was used to describe the
internal vibration of a diatomic molecule. With the help of the
expression for bound state energy levels, a more generalized equation
for the upper bound vibrational quantum number and canonical partition
function were obtained for the diatomic system. The obtained partition
function was used to derive analytical equation for the prediction of
constant pressure (isobaric) molar heat capacity of diatomic molecules.
The analytical model was used to predict the constant pressure molar
heat capacity data of the ground state CO, BBr, HBr, HI, P2, KBr, Br2,
PBr, SiO and Cl2 molecules. The upper bound vibrational quantum number
obtained for the molecules are 85, 100, 21, 21, 115, 301, 89, 157, 110
and 67. The computed average absolute deviation are 2.3462%, 1.1342%,
2.3350%, 1.9078%, 0.7268%, 2.4041%, 1.7849%, 1.8989%, 2.5209% and
2.1523%. The present results are in good agreement with available
literature data on gaseous molecules.