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The nature of the chemical bond in UO 2
Author(s) -
Maslakov Konstantin I.,
Teterin Yury A.,
Ryzhkov Mikhail V.,
Popel Aleksej J.,
Teterin Anton Yu.,
Ivanov Kirill E.,
Kalmykov Stepan N.,
Petrov Vladimir G.,
Farnan Ian
Publication year - 2019
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.26040
Subject(s) - chemical bond , molecular orbital , chemistry , covalent bond , ionic bonding , core electron , x ray photoelectron spectroscopy , valence (chemistry) , valence bond theory , valence electron , molecular orbital diagram , orbital hybridisation , photoemission spectroscopy , molecular orbital theory , atomic orbital , ligand field theory , three center two electron bond , electron , atomic physics , molecule , physics , ion , nuclear magnetic resonance , organic chemistry , quantum mechanics
The nature of the chemical bond in UO 2 was analyzed taking into account the X‐ray photoelectron spectroscopy (XPS) structure parameters of the valence and core electrons, as well as the relativistic discrete variation electronic structure calculation results for this oxide. The ionic/covalent nature of the chemical bond was determined for the UO 8 (D 4h ) cluster, reflecting uranium's close environment in UO 2 , and the U 13 O 56 and U 63 O 216 clusters, reflecting the bulk of solid uranium dioxide. The bar graph of the theoretical valence band (from 0 to ~35 eV) of XPS spectrum was built such that it was in satisfactory agreement with the experimental spectrum of a UO 2 single crystalline thin film. It was shown that unlike the crystal field theory results, the covalence effects in UO 2 are significant due to the strong overlap of the U 6p and U 5f atomic orbitals with the ligand orbitals, in addition to the U 6d atomic orbital (AO). A quantitative molecular orbital (MO) scheme for UO 2 was built. The contribution of the MO electrons to the chemical bond covalence component was evaluated on the basis of the bond population values. It was found that the electrons of inner valence molecular orbitals (IVMO) weaken the chemical bond formed by the electrons of outer valence molecular orbitals (OVMO) by 32% in UO 8 and by 25% in U 63 O 216 .