Molecular structure and analytical potential energy function of SeCO

The density functional method(B3P86/6-311G) is used for calculating the possible structures of SeC, SeO, and SeCO molecules. The result shows that the ground state of the SeC molecule is1Σ, the equilibrium nuclear distance is RSeC= 0.1699 nm, and the dissociation energy is De = 8.7246 eV. The ground state of the SeO molecule is3Σ, with equilibrium nuclear distance RSeO= 0.1707 nm and dissociation energy De = 7.0917 eV. There are two structures for the ground state of the SeCO molecule: Se=C=O and Se=O=C. The linear Se=C=O is1Σ. Its equilibrium nuclear distances and dissociation energy are RSeC= 0.1715 nm, RCO= 0.1176 nm and 18.8492 eV, respectively. The other structure Se=O=C is1Σ. Its equilibrium nuclear distances and dissociation energy are RCO= 0.1168 nm, RSeO= 0.1963 nm and 15.5275 eV,respectively. The possible dissociative limit of the SeCO molecule is analyzed. The potential energy function for the SeCO molecule has been obtained from the many-body expansion theory. The contour of the potential energy curve describes the structure characters of the SeCO molecule. Furthermore, contours of the molecular stretching vibration based on this potential energy function are discussed.