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Previously, various symmetry-adapted (SA) and broken-symmetry (BS) computations have been performed for strongly correlated transition metal species so as to examine magnetic properties in simple cluster models such as binuclear transition metal oxides. Though SA computations such as the complete active space configuration interaction and CASSCF are desirable for estimating physical constants, these computations are heavy for larger cluster models with strongly correlated electrons. K[SUB2]NiF[SUB4] is known to be the two-dimensional perovskite-type antiferromagnet and to have the electronic configuration similar to that of La[SUB2]CuO[SUB4]. Here, we have examined the utility and applicability of the BS spin-polarized hybrid-density functional theory (HUDFT) for cluster models of K[SUB2]NiF[SUB4]. As the result, HUDFT calculation such as UB2LYP has provided the reasonable effective exchange integral (J[SUBab]) followed by our approximately spin projected scheme, in comparison to the experimental one. It was also found that the square planar tetranuclear model has provided the most reasonable J[SUBab] value by HUDFT. In addition, external effects such as putting point charges around cluster models and changing distances between nickel and fluorine have been also examined. The natural orbital analysis by HUDFT has been carried out to obtain natural orbitals and their occupation numbers. Charge density, spin density, and chemical indices expressed by the occupation numbers have been also obtained to elucidate the nature of the chemical bonds in the K[SUB2]NiF[SUB4]-type solids. [ABSTRACT FROM AUTHOR]

At room temperature, cubic SrTiO3perovskite exhibits only paraelectric property, although ferroeletric properties appear in tetragonal BaTiO3and PbTiO3. In this study, the new high-performance ferroelectric such as SrTiO2C perovskite was theoretically designed. Cluster model calculations based on hybrid density functional theory were performed to clarify a ferroelectric mechanism of SrTiO2C. It has been concluded that SrTiO2C can be utilised for a ferroelectric material of a high-speed memory, due to the extremely small polarisation-inversion energy. [ABSTRACT FROM PUBLISHER]

Hybrid Kohn-Sham calculations are performed to clarify the proton-conduction mechanism in Sc-doped SrTiO3 perovskite, from the viewpoint of energetics and bonding. The calculated potential energy curves are discussed and a molecular-orbital analysis performed. Much hydrogen can exist around doped scandium, where it is energetically stabilized. However, scandium-doping has no energetic advantage in the activation energy for proton-conduction. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

We theoretically designed the new sodium ion-conductors such as NaAlO(CN)2 and NaxAl1-x/3(CN)3 perovskite. From the viewpoint of the energetics and bonding, the sodium ion-conductive mechanism was investigated for LaAlO3, NaAlO(CN)2, and NaxAl1-x/3(CN)3 perovskite. It was concluded that NaAlO(CN)2 perovskite can be utilized as a sodium ion-conductor for sodium-sulfur battery. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Previously, we demonstrated that the lithium ion conduction in the perovskite-type manganese fluoride is attributed to counter cation-site vacancy mechanism. The divalent counter cation-doped KxBa(1-x)/2MnF3 was theoretically predicted as the lithium ion conductor in the perovskite-type manganese fluoride. In this study, we considered the oxygen doping for KxBa(1-x)/2MnF3 to realize the higher lithium ion conductivity. It is because lithium ion forms the stronger ionic bond with the doped oxygen anion. The hybrid-DFT calculations were performed to investigate the lithium ion conduction in the oxygen-doped KxBa(1-x)/2MnF3. The calculation results were discussed from the viewpoints of the potential energy curve, electron densities, and charge and spin densities. The effect of the lithium ion fluctuation was also discussed by calculating the ratio of the diffusion coefficients. Finally, we theoretically predicted the ideal oxygen-doped structure for KxBa(1-x)/2MnF3. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009 [ABSTRACT FROM AUTHOR]

Previously, we demonstrated that the lithium ion conduction in the perovskite-type manganese fluoride is attributed to counter cation-site vacancy mechanism. The divalent counter cation-doped KxBa(1-x)/2MnF3 was theoretically predicted as the lithium ion conductor in the perovskite-type manganese fluoride. In this study, we considered the oxygen doping for KxBa(1-x)/2MnF3 to realize the higher lithium ion conductivity. It is because lithium ion forms the stronger ionic bond with the doped oxygen anion. The hybrid-DFT calculations were performed to investigate the lithium ion conduction in the oxygen-doped KxBa(1-x)/2MnF3. The calculation results were discussed from the viewpoints of the potential energy curve, electron densities, and charge and spin densities. The effect of the lithium ion fluctuation was also discussed by calculating the ratio of the diffusion coefficients. Finally, we theoretically predicted the ideal oxygen-doped structure for KxBa(1-x)/2MnF3. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009 [ABSTRACT FROM AUTHOR]

Abstract: We performed the hybrid-density functional theory (DFT) calculations for the strongly correlated perovskite-type manganese fluorides of KMnF3, RbMnF3 and K1− x Li x MnF3 In both solids, UBHHLYP, which contains 50% Hartree–Fock exchange term, provided the reasonable effective exchange integral (Jab ) values, in comparison with the experimental ones. In order to investigate the intrinsic roles of counter cations precisely, we examined the variations of the total energy and Jab value, assuming the displacement of counter cation toward <100> direction. In KMnF3 (RbMnF3), it was found that the steric repulsion between potassium (rubidium) and bottleneck is large, while that between lithium and bottleneck is negligible in K1− x Li x MnF3. Finally, we also showed the possibility of the lithium ion conduction in the antiferromagnetic K1− x Li x MnF3. It was concluded that the lithium ion conduction in RMnF3 is possible, if the vacancy at R site exists. [Copyright &y& Elsevier]

Abstract: We performed hybrid-DFT calculations for La2/3− x Li3x TiO3 (LLT) with lithium ion conductivity, in order to investigate the detailed lithium ion conductive mechanism from the viewpoint of molecular orbital (MO) method. It was concluded that the very ionic lithium ion in bottleneck accelerates the lithium ion conduction. The calculated MO shows no chemical bonding between lithium ion and other ions. In comparison with the perovskite-type trivalent titanium oxide of LaTiO3, the effect of the titanium''s reduction was also investigated. We showed the possibility of the high lithium conductivity in LaTiO3. [Copyright &y& Elsevier]

When we estimate the proper bandgap for the perovskite-type titanium oxide of SrTiO3 by the use of hybrid-density functional theory (DFT) method, it is important to choose the exchange and correlation functionals. Especially, Hartree-Fock (HF) exchange functional plays the major role in inclusion of the localization effect. In this study, we empirically determined the proper HF exchange functional coefficient for SrTiO3. Though the blue-light emission process in SrTiO3 has attracted much interest, the mechanism is still unclear. To elucidate the mechanism of the blue-light emission process, we performed hybrid-DFT calculations for the oxygen deficient cluster models. It was concluded that oxygen deficiency is irrelevant to the process, because of the strong chemical bond between titaniums. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 [ABSTRACT FROM AUTHOR]

When we estimate the proper bandgap for the perovskite-type titanium oxide of SrTiO3 by the use of hybrid-density functional theory (DFT) method, it is important to choose the exchange and correlation functionals. Especially, Hartree-Fock (HF) exchange functional plays the major role in inclusion of the localization effect. In this study, we empirically determined the proper HF exchange functional coefficient for SrTiO3. Though the blue-light emission process in SrTiO3 has attracted much interest, the mechanism is still unclear. To elucidate the mechanism of the blue-light emission process, we performed hybrid-DFT calculations for the oxygen deficient cluster models. It was concluded that oxygen deficiency is irrelevant to the process, because of the strong chemical bond between titaniums. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 [ABSTRACT FROM AUTHOR]

In the perovskite-type titanium oxides, the changes of magnetic properties by GdFeO3-type lattice distortion are observed. In this study, we have performed cluster model calculations based on the density functional theory method, and have obtained the effective exchange integral (Jab) in order to elucidate the magnetic change by the GdFeO3-type lattice distortion. The components of deciding the orbital ordering and magnetic property have also been discussed. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 [ABSTRACT FROM AUTHOR]

In the perovskite-type titanium oxides, the changes of magnetic properties by GdFeO3-type lattice distortion are observed. In this study, we have performed cluster model calculations based on the density functional theory method, and have obtained the effective exchange integral (Jab) in order to elucidate the magnetic change by the GdFeO3-type lattice distortion. The components of deciding the orbital ordering and magnetic property have also been discussed. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 [ABSTRACT FROM AUTHOR]