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Iwata S.,Toyota Physical and Chemical Research Institute
Journal of Physical Chemistry A | Year: 2010

The efficient code to evaluate the molecular interaction energy at the Hartree-Fock level of theory is developed. The method is the third-order single excitation perturbation theory based on the locally projected (LP) molecular orbitals (MO). It is shown that with a proper scaling of the molecular orbital integrals the basis set superposition error can be under controll even with a small size of basis sets. If the basis set contains augmented diffuse functions, the interaction energy, close to the counterpoise corrected energy, can be directly evaluated without the scaling, as fast as a single supermolecule Hartree-Fock calculation. The key of the method is to use the absolutely local occupied and excited MOs. With these MOs, the amount of the charge-transfer (CT) and the energy contribution of the CT terms are evaluated. © 2010 American Chemical Society.


Iwata S.,Toyota Physical and Chemical Research Institute
Journal of Chemical Physics | Year: 2011

The dispersion terms are evaluated with the perturbation theory based on the locally projected molecular orbitals. A series of model systems, including some of the S22 set, is examined, and the calculated binding energies are compared with the published results. The basis set dependence is also examined. The dispersion energy correction is evaluated by taking into account the double excitations only of the dispersion type electron configurations and is added to the 3rd order single excitation perturbation energy, which is a good approximation to the counterpoise (CP) corrected Hartree-Fock (HF) binding energy. The procedure is the approximate CP corrected HF D method. It ensures that the evaluated binding energy is approximately free of the basis set superposition error without the CP procedure. If the augmented basis functions are used, the evaluated binding energies for the predominantly dispersion-bound systems, such as rare gas dimers and halogen bonded clusters, agree with those of the reference calculations within 1 kcalmol-1 (4 kJmol -1). The limitation of the present method is also discussed. © 2011 American Institute of Physics.


Matsuura H.,University of Tokyo | Miyake K.,Toyota Physical and Chemical Research Institute
Journal of the Physical Society of Japan | Year: 2013

The effects of a spin-orbit interaction on transition-metal ions of (4d)3- and (5d)3-based oxides in which three electrons occupy t2g orbitals are studied. The amplitude of the magnetic moment of d electrons on the 5d and 4d orbitals is estimated by numerical diagonalization. It is found that the magnetic moment is reduced by the spin-orbit interaction. It is suggested that (4d)3- and (5d) 3-based oxides are located in the middle of the L-S and J-J coupling schemes. © 2013 The Physical Society of Japan.


Watanabe S.,Kyushu Institute of Technology | Miyake K.,Toyota Physical and Chemical Research Institute
Journal of the Physical Society of Japan | Year: 2013

The mechanism of emergence of robust quantum criticality in Yb- and Ce-based heavy electron systems under pressure is analyzed theoretically. By constructing a minimal model for quasicrystal Yb15Al 34Au51 and its approximant, we show that quantum critical points of the first-order valence transition of Yb appear in the ground-state phase diagram with their critical regimes being overlapped to be unified, giving rise to a wide quantum critical regime. This well explains the robust unconventional criticality observed in Yb15Al34Au 51 under pressure. We also discuss broader applicability of this mechanism to other Yb- and Ce-based systems such as β-YbAlB4 showing unconventional quantum criticality. © 2013 The Physical Society of Japan.


Yakushi K.,Toyota Physical and Chemical Research Institute
Crystals | Year: 2012

This paper reviews charge ordering in the organic conductors, β″-(BEDT-TTF) (TCNQ), θ-(BEDT-TTF)2X, and α-(BEDT-TTF)2X. Here, BEDT-TTF and TCNQ represent bis(ethylenedithio)tetrathiafulvalene and 7,7,8,8-tetracyanoquinodimethane, respectively. These compounds, all of which have a quarter-filled band, were evaluated using infrared and Raman spectroscopy in addition to optical conductivity measurements. It was found that β″-(BEDT-TTF)(TCNQ) changes continuously from a uniform metal to a chargeordered metal with increasing temperature. Although charge disproportionation was clearly observed, long-range charge order is not realized. Among six θ-type salts, four compounds with a narrow band show the metal-insulator transition. However, they maintain a large amplitude of charge order (Δρ~0.6) in both metallic and insulating phases. In the X = CsZn(SCN)4 salt with intermediate bandwidth, the amplitude of charge order is very small (Δρ < 0.07) over the whole temperature range. However, fluctuation of charge order is indicated in the Raman spectrum and optical conductivity. No indication of the fluctuation of charge order is found in the wide band X = I3 salt. In α-(BEDT-TTF)2I3 the amplitude of charge order changes discontinuously from small amplitude at high temperature to large amplitude (Δρmax~0.6) at low temperature. The long-range chargeordered state shows ferroelectric polarization with fast optical response. The fluctuation of multiple stripes occurs in the high-temperature metallic phase. Among α-(BEDTTTF) 2MHg(SCN)4 (X = NH4, K, Rb, Tl), the fluctuation of charge order is indicated only in the X = NH4 salt. α′-(BEDT-TTF)2IBr2 shows successive phase transitions to the ferroelectric state keeping a large amplitude of charge order (Δρmax~0.8) over the whole temperature range. It was found that the amplitude and fluctuation of charge order in these compounds is enhanced as the kinetic energy (bandwidth) decreases. © 2011 by the authors; licensee MDPI, Basel, Switzerland.

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