Theoretical Studies On The Structure And Reactivity Of Several Thorium Clusters And Thorium Oxide Clusters

Thorium,as an important actinide metal,has a close relationship with the nuclear industry.In addition,the thorium oxides have many applications in the field of electrode materials,refractory materials and industrial catalysts.Therefore,the deep researches on thorium and thorium oxide are very meaningful to the understanding of the properties of these materials.We are interest in exploring the geometric and electronic structure,chemical bonding and structural evolution of clusters,and then figuring out the active sites of catalysts reactions at the molecular level,which can give theoretical support for designing novel catalysts and regulating catalytical performance.In this dissertation,we report the theoretical studies on a series of thorium clusters and thorium oxide clusters.A summary of the work is given as following:1.Theoretical calculations are carried out to identify the electronic and structural properties of a series of thorium clusters Thn-/0(n =2-5).With the increasing size of ThN-(n=2-5),the structural evolution is also investigated.Generalized Koopmans'theorem is applied to predict the vertical detachment energies(VDEs)and simulate the photoelectron spectra(PES)of anionic ground states.The results show that the Thn-/0(n= 2-5)clusters prefer open shell electronic configuration.Tn2-and Th3-possess linear structure and triangle structure,respectively.Adding capping thorium atoms to the triangle structure Th3-successively yield the ground states of Th4-and Th5-.2.Density functional theory(DFT)calculations are employed to investigate a series of stoichiometric thorium oxide clusters(ThO2)n-/0(n=1-5),including determining the electronic and structural properties,analyzing the chemical bonding and simulating photoelectron spectroscopy.According to our calculations,the ground states of(ThO2)n-/0(n = 1-5)clusters prefer to form the low-spin structures.With the increasing of the cluster size,the characters of the(ThO2)n(n= 1-5)clusters evolve into ThO2 bulk material.The Th=0 bonds in(ThO2)n(n=1-5)clusters lengthen with the increase.of cluster-size,and-the vibration frequencies of the Th=O decreaseaccordingly.3.Based on the theoretical study of electronic and structural properties of the(ThO2)n-/0(n= 1-5)clusters,density functional theory(DFT)calculations are carried out to investigate the reactivity of the(Th02)n(n = 1-5)clusters.There are some similarities in the reaction mechanisms of thorium oxygen clusters with different sizes:The H2O molecule directly attack the metal thorium atom by oxygen atom,subsequently one of the hydrogen atoms in H2O molecule transfers to the terminal oxygen atom and then the hydroxide ThnO2n-1(OH)2 are formed.The calculation results have shown that all of the above reations are exothermic,indicating that the thorium oxides have potential application prospects in water-splitting reactions.