Mechanistic Aspects of the Reaction of Th+ and Th2+ with Water in the Gas Phase

Ab Initio Density Functional Theory Calculation: Americium Hydrolysis Mechanism

The hydrolysis mechanism of americium was calculated using density functional theory, and the detailed microscopic reaction mechanism was obtained. The results show that americium reacts with water along the octet state to produce oxides and H2, and that this reaction is exothermic. The interaction between Am and O atoms gradually changes from initially electrostatic interaction to covalent interaction, and continues to strengthen. During the reaction process, Am atoms always lose electrons, the 5f orbital is obviously involved, and there is df orbital hybridization. This study provides the necessary theoretical data support for the theoretical and experimental study of the actinide system.

Guided Ion Beam and Quantum Chemical Investigation of the Thermochemistry of Thorium Dioxide Cations: Thermodynamic Evidence for Participation of f Orbitals in Bonding

Kinetic energy dependent reactions of ThO⁺ with O₂ are studied using a guided ion beam tandem mass spectrometer. The formation of ThO₂⁺ in the reaction of ThO⁺ with O₂ is observed to be slightly endothermic and also exhibits two obvious features in the cross section. These kinetic energy dependent cross sections were modeled to determine a 0 K bond dissociation energy of D₀(OTh⁺-O) = 4.94 ± 0.06 eV. This value is slightly larger but within experimental uncertainty of less precise previously reported experimental values. The higher energy feature in the ThO₂⁺ cross section was also analyzed and suggests formation of an excited state of the product ion lying 3.1 ± 0.2 eV above the ground state. Additionally, the thermochemistry of ThO₂⁺ was explored by quantum chemical calculations, including a full Feller-Peterson-Dixon (FPD) composite approach with correlation contributions up to CCSDT(Q) and four-component spin-orbit corrections, as well as more approximate CCSD(T) calculations including semiempirical estimates of spin-orbit energy contributions. The FPD approach predicts D₀(OTh⁺-O) = 4.87 ± 0.04 eV, in good agreement with the experimental value. Analogous FPD results for ThO⁺, ThO, and ThO₂ are also presented, including ionization energies for both ThO and ThO₂. The ThO₂⁺ bond energy is larger than those of its transition metal congeners, TiO₂⁺ and ZrO₂⁺, which can be attributed partially to an actinide contraction, but also to contributions from the participation of f orbitals on thorium that are unavailable to the transition metal systems.

Activation of Water by Thorium Cation: A Guided Ion Beam and Quantum Chemical Study

The reaction of atomic thorium cations with deuterated water as a function of kinetic energy from thermal to 10 eV was studied using guided ion beam tandem mass spectrometry. At thermal energies, both ThO⁺ + D₂ and DThO⁺ + D are formed in barrierless exothermic processes and reproduce results in the literature obtained using ion cyclotron resonance mass spectrometry. As the energy is increased, the branching ratio between these two channels changes such that the dominant product changes from ThO⁺ to DThO⁺ and back to ThO⁺, until ThD⁺ + OD is energetically available and is the dominant product channel. To help understand these experimental results, a variety of theoretical approaches were tried and used to establish a potential energy surface, which compares well with previous theoretical studies. Utilizing the theoretical results, the kinetic energy dependent branching ratio between the ThO⁺ + D₂ and DThO⁺ + D channels was calculated using both RRKM and phase space theory (PST). The results indicate that consideration of angular momentum conservation (as in PST) and spin-orbit corrected energies are needed to reproduce experimental results quantitatively. The PST modeling also provides relative energies for the two competing transition states that lead to the primary products, for which theory provides reasonable agreement. Graphical Abstract Note: This data is.

Gas-phase COS activation by U+: Reaction mechanisms and bonding analysis

Density functional theory (DFT) calculations were used to investigate the gas phase reaction of U[Formula: see text] with COS to produce US[Formula: see text]CO and UO[Formula: see text]CS. It is shown that the two reactions are exothermic and the formation of UO[Formula: see text]CS has the lower energy barrier which agrees with the experimental result that UO[Formula: see text] is the main product. The reaction mechanisms and the potential energy profiles (CPEPs) considering different spin states were presented in detail. Diverse analyses including atoms in molecules, natural bond orbital were used to study the bonding properties of all the involved species.

Ab initio molecular dynamics study of the interaction of plutonium with oxygen in the gas phase

There are two kinds of plutonium surface corrosion, one of which is oxidation between plutonium and oxygen or oxygen compounds.

Ab initio molecular dynamics study of the reaction of U+ and U2+ with H2O in the gas phase: direct classical trajectory calculations

The gas phase reactions of U(+) and U(2+) with H2O were investigated using an ab initio molecular dynamics method. All of the information along the minimum energy path were calculated with density functional theory (DFT) and coupled cluster methods. For U(+) with H2O, the molecular dynamics simulations yield a branching ratio of 86% for the H2 elimination channel to 14% for the H atomic elimination channel in agreement with the quadruple ion trap mass spectrometry (QIT/MS) experimental ratio of 91% to 9%. In the case of U(2+) + H2O, there is a crossing of the potential energy surfaces (PES) after the first transition state. Crossing seams between the PES and possible spin inversion processes were studied by means of the intrinsic reaction coordinate (IRC) approach. For U(2+) with H2O, all trajectories are corresponds to H atom elimination channel, this is consistent with the Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) experimental results. The chemical bonding evolution along the reaction pathways was discussed by using topological methodologies of the electron localization function (ELF).

Water adsorption on platinum dioxide and dioxygen complex: matrix isolation infrared spectroscopic and theoretical study of three PtO(2)-H(2)O complexes

The interactions of water molecule with platinum dioxygen complex and dioxide molecule are investigated by means of matrix isolation infrared spectroscopy and density functional calculations. The platinum atoms reacted with dioxygen to form the previously reported Pt(O(2)) complex. The Pt(O(2)) complex reacted with water molecule to give the Pt(O(2))-H(2)O complex, which was characterized to involve hydrogen bonding between one O atom of Pt(O(2)) and one H atom of H(2)O (structure A). Upon visible light irradiation, the hydrogen bonded Pt(O(2))HOH complex rearranged to another Pt(O(2))-H(2)O isomer (structure B), which involves (O(2))PtOH(2) interaction. The Pt(O(2))-H(2)O complex in structure B can be isomerized to the weakly bound platinum dioxide-water complex (structure C) under UV irradiation.

Topological analysis of the reaction of uranium ions (U+, U2+) with N2O in the gas phase

Density functional theory calculations were performed to study the ability of uranium cations, U(+) and U(2+), to activate the N-N and N-O bonds of N(2)O. A close description of the reaction pathways leading to different reaction products is presented. The obtained results are compared with previous experimental works. The nature of the bonding of all the involved species and the bonding evolution along the reaction pathways was studied by means of the topological analysis of the ELF function.