Structural and spectroscopic properties of small Pun （n= 2-5） molecules

The equilibrium structures and the electronic, spectroscopic and thermodynamic properties of small Pun （n = 2- 5） molecules are systematically investigated using the methods of general gradient approximation （GGA） of density functional theory （DFT）. The results show that the bond length of the lowest-energy structure of Pu2 is 2.578 A. The ground state structure of Pu3 is a triangle with D3h symmetry, whereas for Pu4, the ground state structure is a square （D4h） and the spin polarization of 16 for molecule Pu5 with square geometry （D_4h） is the most stable structure. For the ground state structures, the vibrational spectra as well as thermodynamic parameters are worked out. In addition, the values for the highest occupied molecular orbital （HOMO） and the lowest unoccupied molecular orbital （LUMO） along with the energy gap of all the Pu_2-5 structures are presented. The relevant structural and chemical stabilities are predicted.