In this paper the effect of internal degrees of freedom on the limit of metastability is analyzed by the
Molecular Dynamics (MD) method. Oxygen is assumed as the liquid and oxygen molecules are assumed as
both monatomic and diatomic molecules. The Lennard{Jones (LJ) potential is used as the intermolecular
potential for monatomic molecules and 2 Center Lennard{Jones (2CLJ) potential is used as the intermolecular
potential for diatomic molecules. These parameters are determined so that the averaged potentials of the
respective molecules are consistent with each other. Simulations are performed at various states and an
Equation of State (EOS) of each liquid is obtained. The spinodal lines obtained from the respective EOSs
are compared with each other and the effect of molecular orientation in diatomic liquid on the thermodynamic
limit of metastability is investigated. Moreover, the kinetic limit of metastability is also investigated and
the difference between the monatomic and diatomic liquid oxygen is analyzed
