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J Mol Model ; 19(12): 5569-77, 2013 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-24253320

RESUMO

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.


Assuntos
Entropia , Oxigênio/química , Termodinâmica , Absorção , Elétrons , Metabolismo Energético , Temperatura Alta , Espectroscopia de Ressonância Magnética , Teoria Quântica , Análise Espectral Raman , Vibração
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