DETERMINING THE DENSITY-OF-STATES AND PARTITION-FUNCTION FOR POLYATOMIC-MOLECULES

Absolute thermodynamic properties can be extracted for complex molecules which are described algebraically. By exploiting some group theoretical properties of the Hamiltonians, which often include large anharmonicities, the partition function, and properly normalized density of states can be found. When the first few energies of the system are known, one can extend the results accurately to zero temperature. Examples are given for diatomic molecules as well as the polyatomic molecule C2H2.