Institute for Solid State Physics

Kashiwa, Japan

Institute for Solid State Physics

Kashiwa, Japan
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Ebihara T.,University of Shizuoka | Tsuchiya M.,University of Shizuoka | Saitoh Y.,University of Shizuoka | Jatmika J.,University of Shizuoka | And 4 more authors.
Journal of Physics: Conference Series | Year: 2017

We measured temperature dependence of electrical resistivity and the specific heat as a function of magnetic field up to 8 T in CeAl2. At the metamagnetic transition around 6 T, the coefficient A (ρ ∞ AT2) and Sommerfeld coefficient reduce by 25 %. Such non drastic reduction implies magnetically insensitive phonon could enhance the A and γ in CeAl2 even in low temperature. © Published under licence by IOP Publishing Ltd.


Ochi M.,University of Tokyo | Sodeyama K.,Japan International Center for Materials Nanoarchitectonics | Sodeyama K.,Japan Science and Technology Agency | Sakuma R.,Chiba University | And 3 more authors.
Journal of Chemical Physics | Year: 2012

The transcorrelated (TC) method is one of the promising wave-function-based approaches for the first-principles electronic structure calculations. In this method, the many-body wave function is approximated as the Jastrow-Slater type and one-electron orbitals in the Slater determinant are optimized with a one-body self-consistent-field equation such as that in the Hartree-Fock (HF) method. Although the TC method has yielded good results for both molecules and solids, its computational cost in solid-state calculations, being of order O(N k3N b3) with N k and N b the respective numbers of k-points and bands, has for some years hindered its wide application in condensed matter physics. Although an efficient algorithm was proposed for a Gaussian basis set, that algorithm is not applicable to a plane-wave basis that is suited to and widely used in solid-state calculations. In this paper, we present a new efficient algorithm of the TC method for the plane-wave basis or an arbitrary basis function set expanded in terms of plane waves, with which the computational cost of the TC method scales as O(N k2N b2). This is the same as that of the HF method. We applied the TC method with the new algorithm to obtain converged band structure and cell parameters of some semiconductors. © 2012 American Institute of Physics.


Ochi M.,University of Tokyo | Sodeyama K.,Kyoto University | Sodeyama K.,Japan International Center for Materials Nanoarchitectonics | Tsuneyuki S.,University of Tokyo | Tsuneyuki S.,Institute for Solid State Physics
Journal of Chemical Physics | Year: 2014

Based on the random-phase approximation and the transcorrelated (TC) method, we optimize the Jastrow factor together with one-electron orbitals in the Slater determinant in the correlated wave function with a new scheme for periodic systems. The TC method is one of the promising wave function theories for first-principles electronic structure calculation, where the many-body wave function is approximated as a product of a Slater determinant and a Jastrow factor, and the Hamiltonian is similarity-transformed by the Jastrow factor. Using this similarity-transformed Hamiltonian, we can optimize the one-electron orbitals without evaluating 3N-dimensional integrations for the N-electron system. In contrast, optimization of the Jastrow factor within the framework of the TC method is computationally much more expensive and has not been performed for solid-state calculations before. In this study, we also benefit from the similarity-transformation in optimizing the Jastrow factor. Our optimization scheme is tested in applications to some solids from narrow-gap semiconductors to wide-gap insulators, and it is verified that the band gap of a wide-gap insulator and the lattice constants of some solids are improved by this optimization with reasonable computational cost. © 2014 AIP Publishing LLC.


Aoki Y.,Institute for Solid State Physics | Aoki Y.,University of Hyogo | Yamaguchi A.,Institute for Solid State Physics | Suzuki K.,Institute for Solid State Physics | And 2 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

Systematic observations of the magnetically generated fountain pressure in the superfluid H3 e A1 have been carried out in a newly built apparatus designed to reduce the effect of thermal gradients. In the same apparatus, mechanical pumping and filtering of polarized nuclear spins were realized by the pneumatic pumping action of an electrostatically actuated membrane. In both experiments, the measured induced pressure was observed to decay at all temperatures where the A1 phase appeared in magnetic fields up to 13 T and liquid pressures between 1 and 29 bar. The inferred spin-relaxation rate tended to increase as the low-temperature phase boundary with the A2 phase (TC2) was approached. The increase in spin-relaxation rate near TC2 can be explained by the presence of a minority spin condensate in the A1 phase as predicted by Monien and Tewordt and by the application of the Leggett-Takagi theory of spin relaxation in superfluid H3 e. © 2010 The American Physical Society.


Gryaznov D.,Max Planck Institute for Solid State Research | Gryaznov D.,Institute for Solid State Physics | Evarestov R.A.,Saint Petersburg State Polytechnic University | Maier J.,Max Planck Institute for Solid State Research
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

Phonon frequencies at Γ point in nonmagnetic rhombohedral phase of LaCoO3 were calculated using density-functional theory with hybrid exchange correlation functional PBE0. The calculations involved a comparison of results for two types of basis functions commonly used in ab initio calculations, namely, the plane-wave approach and linear combination of atomic orbitals, as implemented in VASP and CRYSTAL computer codes, respectively. A good qualitative, but also within an error margin of less than 30%, a quantitative agreement was observed not only between the two formalisms but also between theoretical and experimental phonon frequency predictions. Moreover, the correlation between the phonon symmetries in cubic and rhombohedral phases is discussed in detail on the basis of group-theoretical analysis. It is concluded that the hybrid PBE0 functional is able to predict correctly the phonon properties in LaCoO3. © 2010 The American Physical Society.


Ochi M.,University of Tokyo | Tsuneyuki S.,University of Tokyo | Tsuneyuki S.,Institute for Solid State Physics
Chemical Physics Letters | Year: 2015

Second-order Møller-Plesset perturbation theory combined with the bi-orthogonal transcorrelated method (BiTC-MP2) was applied to some simple solids for the first time. Correlation energy retrieved with the Jastrow factor significantly changes the results of the BiTC-MP2 method from the traditional MP2 theory using the Hartree-Fock orbitals. Convergence of the BiTC-MP2 method is preferable to that for the HF-MP2 method because the electron correlation is partially retrieved already at the unperturbed BiTC level, which enables practical application of the BiTC-MP2 method to several solids with respect to computational cost. © 2015 Elsevier B.V. All rights reserved.


Ochi M.,University of Tokyo | Tsuneyuki S.,University of Tokyo | Tsuneyuki S.,Institute for Solid State Physics
Journal of Chemical Theory and Computation | Year: 2014

We present a new ab initio method for excited-state calculations based on wave function theory: transcorrelated (TC) method combined with configuration interaction singles (CIS). Conventional CIS with the Hartree-Fock wave function, while a popular method for excited-state calculations of molecular systems, cannot describe electron correlation effects, such as the screening effect in solids, resulting in inaccurate results such as overestimation of the band gap and exciton binding energy. Here, we adopt the TC method, which takes electron correlations into account through a similarity transformation of the Hamiltonian using the Jastrow factor, and combine it with the CIS approximation. We calculate the optical absorption spectra of solid LiF and GaAs as a test, and verify that the present method reproduces the spectra more accurately than the conventional HF-CIS. The excitonic effect is well described with our method. © 2014 American Chemical Society.


Ochi M.,University of Tokyo | Tsuneyuki S.,University of Tokyo | Tsuneyuki S.,Institute for Solid State Physics
Journal of Physics: Conference Series | Year: 2013

The transcorrelated (TC) method is one of the wave-function-based methods used for first-principles electronic structure calculations, and in terms of the computational cost is applicable to solid-state calculation. In this method, a many-body wave function of electrons is approximated as a product of the Jastrow factor and the Slater determinant, and the first-principles Hamiltonian is similarity-transformed by the Jastrow factor. The Schrödinger equation is rewritten as an eigenvalue problem for this similarity-transformed Hamiltonian, from which one obtains a self-consistent field (SCF) equation for optimizing one-electron orbitals in the Slater determinant at low computational cost. In contrast, optimization of the Jastrow factor is computationally much more expensive and has not been performed for solid-state calculation of the TC method before. In this study, we develop a new method for optimizing the Jastrow factor at a reasonable computational cost using the random-phase approximation (RPA) and pseudo-variance minimization. We apply this method to some simple solids, and find that the band gap of a wide-band-gap insulator is much improved by RPA.


Zvejnieks G.,Institute for Solid State Physics | Ibenskas A.,Lithuanian Academy of Sciences | Tornau E.E.,Lithuanian Academy of Sciences
Surface and Coatings Technology | Year: 2014

Kinetic Monte Carlo (KMC) simulations of Au-Ni phase separation in Au/Ni(111) surface alloy during nickel carbonyl formation reaction were performed at room temperature by taking into account realistic rates of Au and Ni adatom diffusion and CO adsorption and desorption, while keeping the rate of nickel carbonyl formation reaction as a free parameter. We also obtained pair and three-body interaction constants between Au and Ni adatoms using the ab initio calculations and demonstrated that their proper choice is crucial for understanding the Au-Ni separation process. Three regimes with qualitatively different Ni-CO reaction propagation kinetics in Au/Ni(111) surface alloy were found by varying the constants of trio-triangle interactions within the limits of their accuracy. The sensitivity of the proposed model to interaction parameters leads to the regimes that differ by step flow rate, Au islands formation mechanism (channel-type or homogenous flow), Au island contamination level by Ni impurities and reaction damping tendency at the reaction front. Nucleation of nickel-free Au islands was observed for a homogeneous step flow pattern, and the corresponding step flow rate is in a good quantitative agreement with existing experimental data. © 2013 Elsevier B.V.


Bocharov D.,Institute for Solid State Physics | Bocharov D.,University of Latvia | Gryaznov D.,Institute for Solid State Physics | Zhukovskii Y.F.,Institute for Solid State Physics | Kotomin E.A.,Institute for Solid State Physics
Surface Science | Year: 2011

The density functional theory is used in a study of point defects on both UN(001) surface and sub-surface layers. We compare the results for slabs of different thicknesses (both perfect and containing nitrogen or uranium vacancies) with a full geometry, electronic and spin density optimization. The electronic charge density re-distribution, density of states, magnetic moments of U atoms and local atomic displacements around defects are carefully analyzed. It is predicted that the vacancies are formed easier on the surface, whereas the property of sub-surface layer does not differ significantly from the central one in the slab. © 2010 Elsevier B.V. All rights reserved.

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