Spin-dependent localized Hartree-Fock density-functional approach for the accurate treatment of inner-shell excitation of close-shell atoms

We present a spin-dependent localized Hartree-Fock (SLHF) density-functional approach for the treatment of the inner-shell excited-state calculation of atomic systems. In this approach, the electron spin-orbitals in an electronic configuration are obtained first by solving Kohn-Sham (KS) equation with SLHF exchange potential. Then a single-Slater-determinant energy of the electronic configuration is calculated by using these electron spin-orbitals. Finally, a multiplet energy of an inner-shell excited state is evaluated from the single-Slater-determinant energies of the electronic configurations involved in terms of Slater's diagonal sum rule. This procedure has been used to calculate the total and excitation energies of inner-shell excited states of close-shell atomic systems: Be, B^+, Ne, and Mg. The correlation effect is taken into account by incorporating the correlation potentials and energy functionals of Perdew and Wang's (PW) or Lee, Yang, and Parr's (LYP) into calculation. The calculated results with the PW and LYP energy functionals are in overall good agreement with each other and also with available experimental and other ab initio theoretical data. In addition, we present some new results for highly excited inner-shell states.Comment: 8 pages and 9 table

Spin-one bosons in low dimensional Mott insulating states

We analyze the strong coupling limit of spin-one bosons in low dimensional Mott insulating states. In 1D lattices, for an odd number of bosons per site ($N_0$), the ground state is a dimerized valence bond crystal state with a two-fold degeneracy; the low lying elementary spin excitations carry spin one. For an even number of bosons per site, the ground state is a nondegenerate spin singlet Mott state. We also argue that in a square lattice in a quantum disordered limit the ground states should be dimerized valence bond crystals for an odd integer $N_0$. Finally, we briefly report results for non-integer numbers of bosons per site in one-dimensional lattices.Comment: 5 pages; discussions on non-integer case have been shortene

First-principles determined charge and orbital interactions in Fe3_3O4_4

The interactions between charge and orbitally ordered $d$-electrons are important in many transition metal oxides. We propose an effective energy model for such interactions, parameterized with DFT+U calculations, so that energy contributions of both electronic and lattice origin can be simultaneously accounted for. The model is applied to the low-temperature phase of magnetite, for which we propose a new ground state structure. The effective interactions on the B-lattice of Fe$_3$O$_4$ can be interpreted in terms of electrostatics and short-range Kugel-Khomskii exchange coupling. The frustration between optimal charge and orbital orderings leads to a complex energy landscape whereby the supercell for the charge ordering, orbital ordering and ionic displacements can all be different.Comment: 15 pages, 4 figure