Many methods are used to optimize possible ground state structures of PO、PO₂ with multi-basis set. It was found that DFT method is the most suitable for calculation of PO,PO₂. For PO free radical, M-S potential energy functional constants are calculated with 6-311G(3df). For PO₂ free radical, equilibrium structure, harmonic frequency, dissociation energy and force constant are calculated with 6-311+G(3df). Potential energy functions of PO₂ are derived from many-body expansion theory. It was pointed out that there is a saddle point in reaction kinetics O+PO→OPO, and a stable PO₂ molecule could be formed as O atom with energy surpassing 0.55 eV. A stable PO₂ molecule could be formed through two equivalent channels over barrier.

Possible ground state structures, harmonic frequency and dissociation energy of SeO_x(x=1,2) free radical are optimized by different methods and base sets included in Gaussian 09. Among them, QCISD(T)/6-311+G(2df) and B3LYP/6-311G(3d2f) are the most suitable for SeO, SeO₂. Calculation results are in good agreement with experiment. For SeO free radical, Murrell-Sorbie potential energy functional constant are calculated, according to which spectral parameters and force constants are shown. It provides basis for further investigation on SeO_x(x=1,2). For SeO₂ free radical, force constants are calculated at the same time. And potential energy functions of SeO₂ are derived with many-body expansion theory. In a symmetric stretching vibration potential energy diagram of SeO₂, saddle points in reaction kinetics O+SeO→SeO₂ in the symmetry dilation potential energy are found. Activation energy is 48.24 kJ·mol^-1. A stable SeO₂ free radical could be formed as O atom with energy surpassing 0.5 eV.

QCISD method is used to optimize possible ground-state structures of PCl and PCl₂ molecule with multiple basis sets. Dissociation energy, harmonic frequency and force constants are calculated with 6-311 + G (dr) and 6-311G (dr) basis sets, respectively. They agree with experimental observations well. Potential energy functions of PCl₂ are derived from many-body expansion theory. Potential energy curves verify structure characteristics and potential depth. Cl+ PCl and P + ClCl based on molecular reaction potential energy surface are discussed. It describes molecular reaction dynamics successfully.