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Molecular Simulations And First-principles Studies On The Structures And Electronic Properties Of Pt Clusters

Posted on:2010-04-10Degree:MasterType:Thesis
Country:ChinaCandidate:X L WangFull Text:PDF
GTID:2121360275458317Subject:Physical chemistry
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Clusters are the agglomerates of a few to a few thousand atoms with relative stability and with a radius smaller than 50 nm.Clusters are the borderland between the microscopic single atom and the macroscopic solid state,exhibiting extraordinary size-dependent physical and chemical properties.One can design new materials using clusters as the building blocks.A number of intense studies have been performed on platinum clusters at the nano/subnanoscales in recent years.Clusters have potential applications as building blocks for functional nanostructure materials,electronic devices,and nanocatalysts,and they can serve as a model for systematic understanding of structure/property evolution.Structural evolution and electronic propertires of medium-sized Ptn(n=15-24) clusters have been explored using an extensive,unbiased search based on genetic algorithm and density functional theory(DFT) methods.In the DFT calculations,exchange-correlation interactions were approximated by the generalized gradient approximation(GGA) with PBE parameterization.A DFT semi-core pseudopotential(DSPP),and a double numerical basis set plus d-polarization functions(DNP),as implemented,in the DMol3 package were employed. We denoted this scheme as PBE/DSPP/DNP.As a whole,the lowest energy structures of Ptn(n=15-24) clusters are likely to form open structural motifs not the atomic closed shell structures.Four kinds of structural motifs,i.e., dodecahedron based(DODB),cuboctahedron based(COB),layered triangular(LT) and cubic configurations have been investigated for the medium-sized Ptn(n=15-24) cluster.The Ptn (n=15-16,19,24) prefer the DODB growth pattern.While the Ptn(n=17-18,20) lean to the LT configuration.The lowest energy structures of Pt21 and Pt23 clusters adopt the cubic structures.Pt22 is a Cs structure.The electronic property of the most stable structures of Ptn(n=15-24) clusters were also studied in detail.For example:the HOMO-LUMO gap,vertical ionization potentials(IPv) on platinum clusters sizes,the spin multiplicities(M=1,3,5) influence on the most stable structures of platinum clusters.The Ptn(n=15,18,24) clusters are suggested to be "magic" clusters by an analysis of their geometric and electronic properties.The most stable of Pt22 cluster is the only one in triplet not singlet state.The correspondence between the density of states and geometry structures were also discussed. The present results provide useful insight into understanding the structural evolution and electronic properties of medium-sized Pt clusters.The platinum clusters considered here give some useful information for the experimental further studies.
Keywords/Search Tags:Platinum Clusters, Density Functional Theory, Geometry Optimization, Electronic Properties
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