First-Principles Study Of The CePt₃P And RE₂O₂Bi Systems

Strongly correlated materials have rich physical properties and are also the main research field of condensed matter physics.In this thesis,we use firstprinciples calculations based on density functional theory to study the nature of the electronic structure of strong correlated system CePt3P and Er2O2Bi containing f electrons.Due to the strong correlation effect between the electrons of the system,we use the local density approximation(LDA)+U method to deal with two materials.For CePt3P,experimental studies have shown that the Kondo effect and antiferromagnetism coexist.The experimental studies did not give the antiferromagnetic configuration of CePt3P.We first constructed two antiferromagnetic configurations and calculated the total energy and magnetic moment under different U and J to determine the possible antiferromagnetic ground state.The calculation results show that the possible antiferromagnetic ground state has the configuration where spins align ferromagnetically within layer and antiferromagnetically between layers,and the magnetic moment is 0.58μB,which is consistent with the antiferromagnetic ground state of CePt3Si.We then calculated the possible ground state band structure and density of states without and with the spin-orbit coupling(SOC),respectively.Near the Fermi level,there are mainly Ce-f,Pt-d,Pt-p and Ce-d orbitals,and some Pt-s and P-p orbitals.In order to analyze the properties of the electronic structure of CePt3P more comprehensively,we have also calculated the band structure and density of states without and with SOC when there are no f electrons.Near the Fermi level,the states are mainly contributed by Pt-d,Pt-p and Ce-d orbitals.Acooding to experimental,Er2O2Bi will be in an antiferromagnetic state below 3K and no Kondo effect is observed.The experimental studies did not give the antiferromagnetic configuration of Er2O2Bi.We first constructed five antiferromagnetic configurations and calculated the total energy and magnetic moment at Ueff=6 eV to determine the possible antiferromagnetic ground state.The calculation results show that the possible antiferromagnetic ground state is the Type-V(magnetic moment in the z-axis direction)magnetic configuration,and the magnetic moment is 2.9 μB.We calculated the band structure of Type-V(magnetic moment in the z-axis direction)magnetic configuration and the band structure of antiferromagnetism in the primitive cell.It can be seen from the band structure that the several energy bands passing through the Fermi level are mainly occupied by Bi-p orbitals,and the Er-f orbitals are greater than or equal to 1 eV above the Fermi level.When the SOC is not considered,the Bi-pz orbital and the Bi-pypx orbital are easily distinguished.After considering SOC,Bi-pz orbital and Bi-pypx orbital are mixed together.This is similar to the properties of other compounds in RE2O2Bi.