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monodentate or bidentate ligands, occur most often in the equatorial plane perpendicular to the linear O=An=O axis, typically generating octahedral, pentagonal bipyramidal, and hexagonal bipyramidal geometries. The trans-oxo uranyl unit was first elucidated by Fankuchen in 1935 [8] and since then hundreds of structural characterizations have been published. Isostructural hexavalent actinyls are also known for neptunyl, plutonyl, and americyl. The An=O bond strength and reduction resistance both decrease across the series U > Np > Pu > Am. The formation of AmO2 2+ requires the use of strong oxidizing agents and is less commonly studied than the other three actinyls. Because of this and in the interest of working with a manageable amount of data, americyl was not included in this thesis study. Actinyls readily form complexes with ionic F – , Cl – , O 2– , OH – , SO 4– , NO 3– , PO4 3– , CO3 2– , and carboxylates, as well as neutral H2O, tetrahydrofuran (thf), and pyridine. Oxygen–containing electron donor ligands such as tributyl and dibutyl phosphates, ketones, and ethers also form strong complexing agents. Such reagents continue to be used on an industrial scale for the extraction and separation of actinides. Chelating ligands are also known to form strong actinide complexes and ongoing investigations into the multidentate chelating abilities of macrocyclic ligands such as crown ethers [2, 9, 10], calixarenes [2, 11], expanded-porphyrins [2, 12-17], and phthalocyanines [2, 17] are adding to this active field of research. Furthering the understanding of the chemistry of the early actinide elements, An = U, Np, and Pu and their common actinyl formations AnO2 n+ (n = 1 or 2) found in aqueous and nonaqueous solutions, is one of the key aims of this research. These elements have been explored to a much lesser extent than those before them in the periodic table. With 8
all the actinides being radioactive and most of them either scarce (therefore expensive to obtain) or toxic, they are often found to be difficult to study experimentally. This creates an opportunity for computational studies to supplement some of the experimental efforts or potentially allows experimentalists to be better informed and prepared to make time saving decisions before proceeding experimentally. Furthermore, the early actinides are among the heaviest elements, containing 90 electrons or more. This is before even considering their molecular forms, thus often leading to very time consuming and often, difficult calculations. With the 5f, 6s, 6d, 7s, and 7p orbitals of these elements all being relatively close in energy and spatial extent [18, 19], the possibility of entirely new bonding schemes often exist [2, 20]. As well, to approach chemical accuracy (< 2 kcal/mol) it is deemed necessary to include electron correlation effects, resulting from electron–electron interactions. Even more importantly scalar and often also spin–orbit relativistic effects must be included [18, 21-24]. 1.3.1 Electronic Configurations of Early Actinides The 5f orbitals are delocalized and less contracted at the beginning of the actinide series than those of the 4f orbitals of the lanthanides and have been shown to play a significant role in the covalent metal–ligand An=O bonding. As the 5f shell fills, the 5f electrons become more localized and the energy levels fall. In the crossover region, at plutonium, where the transition from delocalized to localized takes place the electronic behavior is especially complicated because of the small energy differences between 9
Page 1 and 2: A Density Functional Study of Actin
Page 3 and 4: Acknowledgements I would like to th
Page 5 and 6: 2.1.3 Kohn-Sham Molecular Orbitals
Page 7 and 8: 4.3.1.1 Metal Coordination ........
Page 9 and 10: List of Tables Table 3-1. Calculate
Page 11 and 12: List of Figures Figure 1-1. Radial
Page 13 and 14: List of Copyrighted Material for wh
Page 15 and 16: Eq. or Eqn. equation etc. et cetera
Page 17 and 18: 1.1 Motivation CHAPTER ONE INTRODUC
Page 19 and 20: eactivity of the early actinides wi
Page 21 and 22: appendix, for supplementary materia
Page 23: the exception of depleted uranium s
Page 27 and 28: early actinides the addition of eac
Page 29 and 30: generally considered to be a partia
Page 31 and 32: 1.3.3 Early Actinides and Actinyls
Page 33 and 34: �� CHAPTER TWO GENERAL T
Page 35 and 36: �� f i �� HF ��
Page 37 and 38: investigations into intermediate si
Page 39 and 40: �� 2.1.2 Exchange-Correlation F
Page 41 and 42: �� In ADF Slater type orbitals
Page 43 and 44: �� nucleus by the stabilized ou
Page 45 and 46: �� 2.2.1 The Scalar Four
Page 47 and 48: H � � T �VRECP Vval (2-16) Fo
Page 49 and 50: y a dielectric constant (ε). The d
Page 51 and 52: orders [64, 65] and Hirshfeld atomi
Page 53 and 54: The Hirshfeld charge on an atom A i
Page 55 and 56: Pasilis et al. [73] recently used e
Page 57 and 58: oader goal we look to show that a c
Page 59 and 60: as the core and the remaining elect
Page 61 and 62: 3.3 Results and Discussion The proc
Page 63 and 64: Several other gas-phase isomers of
Page 65 and 66: Figure 3-1. Structural components:
Page 67 and 68: structural parameters (g03 B3LYP/cc
Page 69 and 70: ands of 19 are 1290 cm -1 for the s
Page 71 and 72: types were identified. The third ca
Page 73 and 74: Figure 3-4. Optimized UN4O12 isomer
Page 75 and 76:
Figure 3-5. Optimized UN4O12 isomer
Page 77 and 78:
subject to different interpretation
Page 79 and 80:
covalent/ionic character rather tha
Page 81 and 82:
Figure 3-6. ∆μ (♦, Debye) vers
Page 83 and 84:
3.3.3.4 Bond Lengths, Angles, Bond
Page 85 and 86:
Table 3-4. Calculated bond lengths
Page 87 and 88:
Table 3-6. Calculated Hirschfeld at
Page 89 and 90:
Table 3-7. Calculated vibrational f
Page 91 and 92:
epresented. The proceeding discussi
Page 93 and 94:
3.3.4.2 a-series type 6: a4, a5, a1
Page 95 and 96:
As for the vibrational frequencies,
Page 97 and 98:
shortest Ny=O bond lengths. The one
Page 99 and 100:
Free energies were calculated, for
Page 101 and 102:
After narrowing down our relative G
Page 103 and 104:
For this study, the use of optimize
Page 105 and 106:
These experimental efforts [125, 12
Page 107 and 108:
through observations of period tren
Page 109 and 110:
obtain thermochemistry data, such a
Page 111 and 112:
complementary ferrocenium/ferrocene
Page 113 and 114:
Figure 4-3. Optimized Case 3 comple
Page 115 and 116:
4.3.1.2 Bond Angles, Bond Lengths,
Page 117 and 118:
1.807 to 1.842 Å, representing rel
Page 119 and 120:
Table 4-4. Gas-phase bond lengths f
Page 121 and 122:
As for the Hirshfeld atomic charges
Page 123 and 124:
oxidation states show a noticeable
Page 125 and 126:
62.0º for An VI and An V complexes
Page 127 and 128:
U VI O23, and 0.52 for Np VI O23 ar
Page 129 and 130:
Furthermore with available experime
Page 131 and 132:
somewhat ad hoc values predicted fo
Page 133 and 134:
addition, computational evidence of
Page 135 and 136:
Actinide separations of spent fuels
Page 137 and 138:
PUREX process for the separation of
Page 139 and 140:
DFT wave function should improve th
Page 141 and 142:
Experimental bond lengths for dioxy
Page 143 and 144:
chemically and are rapidly hydrolyz
Page 145 and 146:
A.1.1.6 Dinitrogen Pentoxide In the
Page 147 and 148:
labeled as TS21. The perpendicular
Page 149 and 150:
type 11 containing cis,trans-ON·OO
Page 151 and 152:
Both an NO + and an NO2 ligand can
Page 153 and 154:
Figure A-6. Optimized UN4O12 isomer
Page 155 and 156:
BIBLIOGRAPHY 1. Berard, J.J., Shamo
Page 157 and 158:
38. Lee, C., Yang, W., and Parr, R.
Page 159 and 160:
79. Brouard, M., et al., J. Chem. P
Page 161:
122. Veauthier, J.M., et al., Inorg
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