Theoretical Study Of Pb_nM_n (M=Cu, Ag, Au, Sn And Sb) Clusters

Vacuum metallurgy has many advantages compared with traditional metallurgy,such as environment friendly,simplified flow sheet,high metal recovery,simple equipment,low energy consumption.However,Pb and M?M=Cu,Ag,Au,Sn and Sb?can coexist in recovered metal by separation of lead-based alloys using vacuum metallurgy.In addition,microstructures and properties of Pb-M alloys are scarcely investigated,thus the development of vacuum metallurgy has been limited.Clusters have many unique properties which are ranged from atom,molecule and bulk materials,and alloy clusters can exhibit some essential properties of the corresponding bulk alloys or alloy melts.In this thesis,the ground state structures of Pb_nM_n?M=Cu,Ag,Au,Sn and Sb;n=2-12?clusters were searched by ab initio molecular dynamics.Average binding energies,vertical electron ionization potentials,vertical electron affinities,HOMO-LUMO gaps,average Mulliken charges,and density of states of Pb_nM_n?M=Cu,Ag,Au,Sn and Sb;n=2-12?clusters have been systematically investigated by density functional theory.The main results of this thesis are as follows:?1?The structural evolutions of Pb_nM_n?M=Cu,Ag,Au,Sn and Sb;n=2-12?clusters have been unraveled at an atomic level,M atoms show the trend of bonding together and surrounded by Pb atoms with the increasing cluster size n.?2?The average binding energies of Pb_nM_n?M=Cu,Ag,Au,Sn and Sb;n=2-12?clusters indicate increased trends.The clusters could be served as the ideal candidates to calculate interaction energy parameters in Wilson or UNIQUAC model when the average binding energies of those clusters tend to be stable,and predict the vapor-liquid equilibria for Pb-M?M=Cu,Ag,Au,Sn and Sb?alloy systems.?3?The vertical electron ionization potentials of Pb_nM_n?M=Cu,Ag,Sn?clusters show increased trends,whereas the vertical electron affinities indicate decreased trends with the increasing cluster size n.?4?Overall,the HOMO-LUMO gaps of Pb_nM_n?M=Cu,Ag,Au,Sn and Sb?clusters decrease with the increasing cluster size n,it can be concluded that chemical reactivity of the clusters decrease with the increasing cluster size n.Pb_nCu_n?n=4,8and 11?clusters are the magic clusters of Pb_nCu_n?n=2-14?clusters,Pb_nAg_n?n=4,8and 10?clusters are the magic clusters of Pb_nAg_n?n=2-12?clusters,Pb_nAu_n?n=4,6and 8?clusters are the magic clusters of Pb_nAu_n?n=2-12?clusters,Pb_nSn_n?n=3,6,8and 11?clusters are the magic clusters of Pb_nSn_n?n=2-12?clusters,Pb_nSb_n?n=5 and 9?clusters are the magic clusters of Pb_nSb_n?n=2-12?clusters.?5?According to the average Mulliken charges of Pb atoms and M atoms in Pb_nM_n?M=Cu,Au and Sn?clusters,the charges are always transferred from Pb atoms to M atoms except for Pb₁₀Sn₁₀ clusters.?6?In general,the density of states of Pb_nM_n?M=Cu,Ag,Sn and Sb?clusters shift toward more negative energy levels and the nonlocality of density of states became better with the increasing cluster size n.?7?Pb_nAu_n?n=4,6 and 8?clusters could be regarded as ideal gas sensors for CO and NO gases based on the adsorption properties and electric conductivity changes of Pb_nAu_n?n=4,6 and 8?clusters.This work has provided guidance for calculating vapor-liquid equilibria phase diagrams of Pb-M?M=Cu,Ag,Au,Sn and Sb?alloy systems,vacuum distillation of Pb-M?M=Cu,Ag,Au,Sn and Sb?alloys and theoretical design of Pb-M?M=Cu,Ag,Au,Sn and Sb?nanomaterials.