Theoretical Studies On The Function Of Heavy Metals In Complex Catalyst And Doped Phosphorene Semiconductor Material

The theoretical study,fabrication,modification and related application of functional materials have attracted increasing attention in the material research field.In the present article,the novel catalyst and dilute magnetic semiconductor containing heavy metals are modeled by using the methods of coordination and doping.The binuclear cyclopentadienylmetal carbonyl hydrides and lanthanide atom doped phosphorene were systemically studied by density functional theory calculation.The main research contents and results are listed as follows:?1?The structures and thermodynamic properties of the Cp₂M₂H₂?CO?_n?M=Ir,Os,Re;n=3,2,1?systems are calculated using the Gaussian 09 program package.These complexes provide examples of binuclear structures having metal-metal bonds of formal orders ranging from zero to four as determined by the 18-electron rule.The low-energy Cp₂Ir₂H₂?CO?₃structures lacking a direct iridium-iridium bond necessarily have a bridging CO group holding together the two iridium atoms.For Cp₂Ir₂H₂?CO?₂,low-energy unbridged structures are found corresponding to the experimental unbridged Cp*₂Ir₂H₂?CO?₂ structure.However,for Cp₂Os₂H₂?CO?₂ the lowest energy structure has two hydrogen atoms bridging the formal Os=Os double bond similar to the experimental doubly bridged Cp*₂Os₂H₂?CO?₂ structure.The lowest energy structures of the monocarbonyls Cp₂M₂H₂?CO?have all three ligands?2H+CO?bridging a central metal-metal bond.The Cp₂Re₂H₂?CO?structures provide examples of both bridged and unbridged structures containing formal Re-Re quadruple bonds with highly bridged structures being preferred energetically.Two binuclear cyclopentadienylmetal carbonyl hydrides are known containing the third-row transition metals,namely Cp*₂Os₂?CO?₂H₂ and Cp*₂Ir₂?CO?₂H₂.According to the thermochemistry analysis,the isolation of Cp₂Ir₂H₂?CO?₂ and Cp₂Os₃H₂?CO?₂ are stable molecules,and Cp₂Os₂H₂?CO?₃ could be viable experimentally.Although none of the Cp₂Re₂H₂?CO?_n?n=3,2,1?derivatives are known experimentally,the CO dissociation energies and structure optimization suggest Cp₂Re₂H₂?CO?₂ to be the most promising synthetic target.?2?The structure and magnetic property of Ln-doped phosphorene?Ln=La,Ce,Pr,Nd,Pm,Eu and Gd?have been calculated using GGA+U method in the Vienna ab initio simulation package?VASP?.In the optimized Ln-doped phosphorene configuration,there are strong bonds between the lanthanide atom and the phosphorene.Doping Ln atoms in phosphorene are energetically favorable and Ln-doped system may be synthesized in the appropriate experimental conditions.The predicted magnetic moments are in the range from1.0?_B to 7.0?_B,proportional to the number of spin-parallel 4f electrons.And the magnetic moment could be as high as 7.0?_B for the Eu-and Gd-doping cases,higher than all the known magnetic moments of the main-group and transition metal-doped systems.The spin charge density and Bader charge analysis reveal the origination of the magnetism contributed mainly by the 4f-orbital electrons of the doping Ln atoms.The calculated electronic structure exhibits that the doping of the La,Ce,Pr,Nd and Gd atoms has little effect on the band structure of the pristine phosphorene.Thus,Ln-doped phosphorene still reserves a semiconducting feature with bandgap values close to pristine phosphorene.And Pm-doped case has the smallest bandgap of 0.77 eV.Interestingly,in the Eu-doped case,a valence band crossing the Fermi level,increasing the hole carrier concentration of the semiconducting phosphorene.We expect that the Ln-doped phosphorene with high and tunable magnetic moment could become a next-generation candidate of potential dilute magnetic semiconductor.