Anharmonic Algebraic Model of Thermodynamic Properties of Diatomic Molecules

An algebraic model based on Lie-algebraic techniques is applied to the analysis of thermodynamic vibrational properties of diatomic molecules. The local anharmonic effects are described by a Morse-like potential and corresponding anharmonic bosons associated with the U(2) algebra. A vibrational high temperature partition function and the related thermodynamic functions are derived in terms of the parameters of the model. The thermal expansion operator is defined and obtained using the renormalized frequency of the model.