The Experts below are selected from a list of 201 Experts worldwide ranked by ideXlab platform
Takashi Mizokawa - One of the best experts on this subject based on the ideXlab platform.
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Impact of Local Lattice Disorder on Spin and Orbital Orders in Ca2-xSrxRuO4
Journal of the Physical Society of Japan, 2013Co-Authors: Takuya Sugimoto, D. Ootsuki, Takashi MizokawaAbstract:We have studied relationship between local lattice disorder, Ru \(4d\) spin–orbit interaction, and global spin/orbital orders of Ca2-xSrxRuO4 in the Sr- and Ca-rich regions of its phase diagram by using unrestricted Hartree–Fock Calculation on a \(8\times 8\) RuO4 lattice model. The Calculations show that the local elongation of RuO6 octahedron in an antiferromagnetic insulator Ca2RuO4 induces local orbital change with making the Mott gap narrower. On the other hand, local compression of RuO6 octahedron in a paramagnetic metal Sr2RuO4 induces global antiferromagnetic or ferromagnetic states. This result is consistent with a recent systematic \(\mu\)SR study by Carlo et al. which has revealed the static antiferromagnetic order at low temperature in the Sr-rich region.
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Spin-Charge-Orbital Ordering in Hollandite-Type Manganites Studied by Model Hartree-Fock Calculation
Journal of the Physical Society of Japan, 2013Co-Authors: Makoto Fukuzawa, D. Ootsuki, Takashi MizokawaAbstract:We have studied spin–charge–orbital orderings in a Mn3+/Mn4+ mixed valence state on a hollandite-type lattice using unrestricted Hartree–Fock Calculation on a multi-band Mn \(3d\)–O \(2p\) lattice model. The Calculations show that all the Mn3+–Mn4+, Mn3+–Mn3+, and Mn4+–Mn4+ superexchange interactions are ferromagnetic and play important roles to stabilize the charge and orbital ordering patterns. The most stable charge and orbital ordering pattern is consistent with the \(1\times 1\times 1\) orthorhombic or monoclinic structure of K1.6Mn8O16.
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Spin-charge-orbital ordering in hollandite-type manganites studied by model Hartree-Fock Calculation
arXiv: Strongly Correlated Electrons, 2013Co-Authors: Makoto Fukuzawa, D. Ootsuki, Takashi MizokawaAbstract:We investigate spin-charge-orbital ordering in a Mn$^{3+}$/Mn$^{4+}$ mixed valence state on a hollandite-type lattice using unrestricted Hartree-Fock Calculation on a multi-band Mn 3$d$-O 2$p$ lattice model. The Calculations show that the Mn$^{3+}$-Mn$^{4+}$ double exchange interaction, the Mn$^{3+}$-Mn$^{3+}$ and Mn$^{4+}$-Mn$^{4+}$ superexchange interactions are ferromagnetic and play important roles to stabilize the charge and orbital ordering pattern. The most stable charge and orbital ordering pattern is consistent with the $1\times1\times1$ orthorhombic or monoclinic structure of K$_{1.6}$Mn$_8$O$_{16}$.
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Optical response and electronic structure of Zn-doped MgAl2O4
Journal of Applied Physics, 2007Co-Authors: Takashi Mizokawa, Eiichi HanamuraAbstract:We have studied the optical response and the electronic structure of Zn-doped MgAl2O4 using optical transmission, emission, and excitation spectroscopies, x-ray photoemission spectroscopy, and unrestricted Hartree-Fock Calculation. Emission lines at 710, 650, and 470nm observed in pure MgAl2O4 are related to the Mg vacancies and Mg–Al antisite defects. Interestingly, the intensities of these emission lines are enhanced by Zn doping. Unrestricted Hartree-Fock Calculation for Zn-doped MgAl2O4 shows that in-gap impurity states are formed just above the valence-band maximum of MgAl2O4 when the Zn ion is substituted for the B-site Al ion. On the other hand, no in-gap state is formed when the Zn ion is substituted for the A-site Mg ion. The position of the Zn (3d) impurity level is identified by the photoemission measurement. The broad spectral features of the defect-induced states in pure MgAl2O4 is dramatically reduced by the Zn doping, indicating that holes supplied from the Zn ions at B site are trapped by ...
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Orbital ordering in La0.5Sr1.5MnO4 studied by model Hartree-Fock Calculation
Physical Review B, 2005Co-Authors: K. Ebata, Takashi Mizokawa, A. FujimoriAbstract:We have investigated orbital ordering in the half-doped manganite La$_{0.5}$Sr$_{1.5}$MnO$_4$, which displays spin, charge and orbital ordering, by means of unrestricted Hartree-Fock Calculations on the multiband $p$-$d$ model. From recent experiment, it has become clear that La$_{0.5}$Sr$_{1.5}$MnO$_4$ exhibits a cross-type $(z^2-x^2/y^2-z^2)$ orbital ordering rather than the widely believed rod-type $(3x^2-r^2/3y^2-r^2)$ orbital ordering. The Calculation reveals that cross-type $(z^2-x^2/y^2-z^2)$ orbital ordering results from an effect of in-plane distortion as well as from the relatively long out-of-plane Mn-O distance. For the "Mn$^{4+}$" site, it is shown that the elongation along the c-axis of the MnO$_6$ octahedra leads to an anisotropic charge distribution rather than the isotropic one.
Ksenia R. Briling - One of the best experts on this subject based on the ideXlab platform.
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Atomic effective potentials for starting molecular electronic structure Calculations.
Theoretical Chemistry Accounts, 2020Co-Authors: Dimitri N. Laikov, Ksenia R. BrilingAbstract:Atomic effective one-electron potentials in a compact analytic form in terms of a few Gaussian charge distributions are developed, for Hydrogen through Nobelium, for starting molecular electronic structure Calculations by a simple diagonalization. For each element, all terms but one are optimized in an isolated-atom Hartree--Fock Calculation, and the last one is parametrized on a set of molecules. This one-parameter-per-atom model gives a good starting guess for typical molecules and may be of interest even on its own.
Dimitri N. Laikov - One of the best experts on this subject based on the ideXlab platform.
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Atomic effective potentials for starting molecular electronic structure Calculations.
Theoretical Chemistry Accounts, 2020Co-Authors: Dimitri N. Laikov, Ksenia R. BrilingAbstract:Atomic effective one-electron potentials in a compact analytic form in terms of a few Gaussian charge distributions are developed, for Hydrogen through Nobelium, for starting molecular electronic structure Calculations by a simple diagonalization. For each element, all terms but one are optimized in an isolated-atom Hartree--Fock Calculation, and the last one is parametrized on a set of molecules. This one-parameter-per-atom model gives a good starting guess for typical molecules and may be of interest even on its own.
D. S. Onley - One of the best experts on this subject based on the ideXlab platform.
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Relativistic Hartree-Fock Calculation of deformed nuclei
Physical review. C Nuclear physics, 1991Co-Authors: Jian-kang Zhang, D. S. OnleyAbstract:Hartree-Fock Calculations are performed for deformed nuclei {sup 20}Ne, {sup 24}Mg, and {sup 28}Si in the relativistic quantum-field-theory framework, the exchange of {sigma}, {omega}, {rho}, and {pi} mesons and photons are included, the coupling constants are adopted from relativistic Hartree-Fock nuclear-matter Calculation. Compared to the Hartree results, binding energies are improved by around 8%; however, no appreciable improvement on the quadrupole moments is observed.
Jan Philip Solovej - One of the best experts on this subject based on the ideXlab platform.
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There Are No Unfilled Shells in Unrestricted Hartree-Fock Theory
Physical Review Letters, 1994Co-Authors: Volker Bach, Michael Loss, Elliott H Lieb, Jan Philip SolovejAbstract:We prove that in an exact, unrestricted Hartree-Fock Calculation each energy level of the Hartree-Fock equation is either completely filled or completely empty. The only assumption needed is that the two-body interaction is—like the Coulomb interaction—repulsive; it could, however, be more complicated than a simple potential; e.g., it could have tensor forces and velocity dependence. In particular, the Hartree-Fock energy levels of atoms and molecules, often called shells, are never partially filled.
