A Systematically Theoretical Study On The Reaction Mechanism Of Th,U With PH₃ And OCS

In recent decades,as the demand for actinides in the nuclear energy industry and nuclear defense continues to grow,researchers pay the growing attention on actinides is increasing,especially uranium,thorium and other actinides and their compounds.Due to the unique physical and chemical properties of actinides in metal chemistry,the research on the corrosion reactions of nuclear materials?actinides and small molecules?,and the process of actinides dissociated the basic bonds of small molecules and other related hot spots has also developed rapidly.However,in practical applications and research,the exploration of actinide elements is still facing difficulties.Actinides have lively chemical properties,and react easily with small molecules in the atmosphere,these reactions will cause corrosion of nuclear materials during storage and use.After corrosion of nuclear materials,firstly,the material itself will deteriorate and affect the use.Secondly,the storage container will be damaged,the surrounding environment will also be affected,which is extremely detrimental to the safe storage and use of nuclear materials.In addition,due to the relatively large atomic number of actinides,and the complexity of the 5f electron orbital in the interaction between atoms,and the effects of relativistic effects on their valence electron movement,the actinides dissociate from the basic bond.The process is complex and it is not adapted to traditional computational chemistry methods.Therefore,using safe and reliable quantum computing chemistry to conduct research,on the one hand,reduce the uncertainties in experimental research and avoid the hazards brought by nuclear materials.on the other hand,it is possible to use theoretical methods to more effectively understand the effect of actinide dissociation of basic bonds?P-H,O-C,C-S?and 5f orbitals in the reaction.These studies are conducive to revealing the nature of actinides,and provide important theoretical foundations for the surface corrosion prevention of nuclear materials and the design and synthesis of new actinides.Based on the density functional theory and transition state theory,this thesis makes a detailed investigation of the reaction of Th,U with PH₃ and OCS,including the reaction mechanism,interatomic interactions and reaction rates of actinides and small molecules.The main contents include the following sections:?1?The density functional theory was used to systematically study the process of U and Th atoms activating the P-H bond of PH₃ molecules to form thorium and uranium phosphine.The main content has a detailed description of the reaction mechanism,including the potential energy profile of the three heavy states and the nature of the interaction and evolution of the ground state atoms,and compared with the experimental results of Andrews group,the results show good consistency.There are two main types of reaction channels for U+PH₃ and Th+PH₃,isomerization channels and dehydrogenation channels.The difference between the two reactions occurs during the first P-H bond dissociation process.These methods including electron local density function?ELF?,atomic quantum theory in the molecule?QTAIM?,Mayer bond order and natural bond orbitals?NBO?was used to understand the characteristics of interatomic interactions in the reaction process.In addition,the reaction rate of each stage was calculated.?2?The second part is a detailed study on the synthesis mechanism of thorium sulfides.The reaction of thorium cation Th2+ with sulfur atom donor OCS to form thorium sulfide and other complexes was mainly explored by density functional theory.The reaction includes two paths: primary reaction and secondary reaction.At the same time,a variety of topological analysis methods including ELF,QTAIM,and Mayer bond levels were used to study the characteristics of multiple bonds and the evolution of bonding in the reaction process.The reaction rate considering the one-dimensional tunneling effect is calculated.The study of the above reactions not only provides theoretical basis for actinide elements and their cations to dissociate similar basic bonds,but also provides reference for us to understand the study of other gas molecules corroding the surface of nuclear materials...