A DFT Investigate On Mn, Fe, Co And Ni-encapsulated Alkali-metal Magnetic Superatoms

Atomic clusters with suitable size and composition attract much attention due to their peculiar properties. Recently, these clusters can be designed to mimic the chemistry of atoms in the Periodic Table, especially the electronic properties of the noble metals. Thus, they are very promising to obtain the new and inexpensive catalytic materials in the domains of new energy resources, comprehensive ecological improvement, and so on. These clusters which can be viewed as "super atoms" have been supported by the study of quantum chemistry. In this dissertation, on the basis of the view about "super atoms", a systemic DFT study on embedded clusters of Mn, Fe, Co and Ni in alkali-metal magnetic superatoms has been investigated, including the structures, stability, electronic configurations and magnetic moments.Chapter one outlines the research progress on "super atoms" meanwhile points out the objects in this dissertation. Chapter two, we briefly introduce the density functional theory and the computational programs used in the dissertation. Chapter three shows and analyses the DFT calculation results about embedded clusters of Mn, Fe, Co and Ni in alkali-metal magnetic superatoms.The main results are lists as follows:1. For Mn@A₈ (A= Li, Na, K, Rb, Cs) clusters, the main results are listed as follows: 1) The lowest-lying geometric configurations of Mn@Cs₈ and Mn@Rb₈ are both with D₂ symmetry; 2) Mn@Li8 displays low binding-energy and large HOMO-LUMO gap, which imply strong stability and chemical inertness; 3) On the analysis of magnetic moments and the spin electronic density, the lowest-lying structures for Mn-embedded Mn@A8(A=K,Rb and Cs) clusters display the magnetic moment of 5.00μB while for Mn@Li8 and Mn@Na8, they have about 3.00μB.2. For Fe@A₈ (A= Li, Na, K, Rb, Cs) clusters, the lowest-lying geometric configurations are both with C₁ symmetry. Meanwhile, the embedding Fe atom is lied in the center of clusters; The lowest-lying structure of Fe@Li clusters have low binding-energy and large HOMO-LUMO gap, which reflect the strong stability and chemical inertness; The value of the spin magnetic moments for Fe@A8 (A= K, Rb, Cs) is 4.00μB.3. For Co@A₈ (A= Li, Na, K, Rb, Cs) clusters, the calculations show that: the lowest-lying structures are similar with Fe@A8, both with C₁ symmetry; The lowest-lying structure of Co@Li clusters have low binding-energy and large HOMO-LUMO gap, which reflect the strong stability and chemical inertness; The value of the spin magnetic moments for Co@A₈ (A= K, Rb) is 3.00μB.4. The DFT calculations for Ni@A₈ (A= Li, Na, K, Rb, Cs) clusters prove that the lowest-lying structure is with C₂ symmetry while the other Ni-embedded clusters are with no symmetry. The lowest-lying structure of Ni@Li clusters has low binding-energy and large HOMO-LUMO gap, which reflect the strong stability and chemical inertness. However, the Ni-embedded alkali-metal clusters have no magnetic moments. By comparison, Mn@A₈(A=K, Rb and Cs) clusters show the same magnetic moments (about 5.00μB). Thus, Mn@A8(A=K, Rb and Cs) is promising to be applied in spintronics and magnetic memory materials since the discovery of the V@Cs₈ magnetic "super atoms".