【摘 要】
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Classical LSDA predicts wrong results about gap for the Mott-Hubbard insulator and charge ordering systems such as Fe3O4,LDA+U and HSE methods are proved to be quite successful in correcting LDA appro
【机 构】
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中国科学院山西煤炭化学研究所,山西省太原市迎泽区桃园南路
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Classical LSDA predicts wrong results about gap for the Mott-Hubbard insulator and charge ordering systems such as Fe3O4,LDA+U and HSE methods are proved to be quite successful in correcting LDA approximation for treating with strong electron-electron correlations.This work concentrates on a systematic comparison of the lattice structures,electronic and optical properties of Fe3O4 and Fe5C2,predicted by density functional theory using PBE,PBE+U and the Heyd-Scuseria-Ernzerhof screened hybrid density functional(HSE).For Fe3O4,they give a consistent ferrimagnetism ground state.PBE+U(U≈4eV)and HSE(μ≈0.207)can produce a good description about structure parameters,magnetic,electronic structure and optical properties.With regard to HSE method,increasing screened constant μ has a little effect on lattice parameters but leads to decreasing Fe magnetic moment and decreasing d-electrons coulomb repulsion.All results obtained using large screened constant μ are close to that in the case of PBE functional.For Fe5C2,ferromagnetism ground state is exactly predicted by three approximations.PBE is a suite approximation predicting about structure parameters,magnetic,electronic structure and optical properties.For HSE,Fe5C2 show the rule analogous to Fe3O4 with μ increasing.A significant conclusion is that we should adopt reasonable screening constant μ combining with the nature of system to accurately predict the material properties by HSE functional.
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