title: Structures, spectroscopic and thermodynamic properties of U₂On (n = 0 ∼ 2, 4) molecules: a density functional theory study.
abstract: The equilibrium structures, spectroscopic and thermodynamic parameters [entropy (S), internal energy (E), heat capacity (C p)] of U₂, U₂O, U₂O₂ and U₂O₄ uranium oxide molecules were investigated systematically using density functional theory (DFT). Our computations indicated that the ground electronic state of U₂ is the septet state and the equilibrium bond length is 2.194 Å; the ground electronic state of U₂O and U₂O₂ were found to be X³Φ and X³Σ(g) with stable C(∞v) and D(∞h) linear structures, respectively. The bridge-bonded structure with D(2h) symmetry and X³B₁(g) state is the most stable configuration for the U₂O₄ molecule. Mulliken population analyses show that U atoms always lose electrons to become the donor and O atoms always obtain electrons as the acceptor. Molecular orbital analyses demonstrated that the frontier orbitals of the title molecules were contributed mostly by 5f atomic orbitals of U atoms. Vibrational frequencies analyses indicate that the maximum absorption peaks stem from the stretching mode of U-O bonds in U₂O, U₂O₂ and U₂O₄. In addition, thermodynamic data of U₂O(n) (n = 0 ∼ 4) molecules at elevated temperatures of 293.0 K to 393.0 K was predicted.
authors.affiliation: Institute of Atomic and Molecular Physics, Sichuan University, Chengdu, 610065, People's Republic of China.
authors.forename: Peng
authors.initials: P
authors.lastname: Li
authors.forename: Wen-Xia
authors.initials: WX
authors.lastname: Niu
authors.forename: Tao
authors.initials: T
authors.lastname: Gao
authors.forename: Fan
authors.initials: F
authors.lastname: Wang
authors.forename: Ting-Ting
authors.initials: TT
authors.lastname: Jia
authors.forename: Da-Qiao
authors.initials: DQ
authors.lastname: Meng
authors.forename: Gan
authors.initials: G
authors.lastname: Li
mesh_terms: D000042:Absorption; D004583:Electrons; D004734:Energy Metabolism; D019277:Entropy; D006358:Hot Temperature; D009682:Magnetic Resonance Spectroscopy; D010100:Oxygen / Q000737:chemistry*; D011789:Quantum Theory; D013059:Spectrum Analysis, Raman; D013816:Thermodynamics; D014732:Vibration
chemical_list: D010100:Oxygen