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Journal Articles

Magnetic skyrmion lattice in 4f electron magnet EuPtSi

Kaneko, Koji; Kakihana, Masashi*; Hedo, Masato*; Nakama, Takao*; Onuki, Yoshichika*

Hamon, 30(3), p.160 - 165, 2020/08

no abstracts in English

Journal Articles

Complexation and bonding studies on [Ru(NO)(H$$_{2}$$O)$$_{5}$$]$$^{3+}$$ with nitrate ions by using density functional theory calculation

Kato, Akane*; Kaneko, Masashi; Nakashima, Satoru*

RSC Advances (Internet), 10(41), p.24434 - 24443, 2020/06

 Times Cited Count:1 Percentile:100(Chemistry, Multidisciplinary)

Complexation reactions of ruthenium-nitrosyl complexes in HNO$$_{3}$$ solution were investigated by density functional theory (DFT) calculations in order to predict the stability of Ru species in high-level radioactive liquid waste (HLLW) solution. Equilibrium structure of [Ru(NO)(NO$$_{3}$$)$$_{3}$$(H$$_{2}$$O)$$_{2}$$] obtained by DFT calculations reproduced the experimental Ru-ligands bond lengths and IR frequencies reported previously. Comparison of the Gibbs energies among the geometrical isomers revealed that the complexation reactions of the ruthenium-nitrosyl complexes with NO$$_{3}$$$$^{-}$$ proceed via the NO$$_{3}$$$$^{-}$$ coordination to the equatorial plane toward the Ru-NO axis. We also estimated Gibbs energy differences on the stepwise complexation reactions to succeed in reproducing the fraction of Ru-NO species in 6 M HNO$$_{3}$$ solution, such as in HLLW, by considering the association energy between the Ru-NO species and the substituting ligands. Electron density analyses of the complexes indicated that the strength of the Ru-ligands coordination bonds depends on the stability of the Ru species and the Ru complex without NO$$_{3}$$$$^{-}$$ at the axial position is more stable than that wit NO$$_{3}$$$$^{-}$$, which might attribute to the difference in the trans influence between H$$_{2}$$O and NO$$_{3}$$$$^{-}$$. Finally, we demonstrated the complexation kinetics in the reactions $$x = 1 rightarrow x = 2$$. The present study is expected to enable us to model the precise complexation reactions of platinum-group metals in HNO$$_{3}$$ solution.

Journal Articles

Magnetic skyrmion lattice in 4$$f$$ electron magnet EuPtSi

Kaneko, Koji; Kakihana, Masashi*; Hedo, Masato*; Nakama, Takao*; Onuki, Yoshichika*

Kotai Butsuri, 54(12), p.757 - 766, 2019/12

no abstracts in English

Journal Articles

Density Functional Theory (DFT)-based bonding analysis correlates ligand field strength with $$^{99}$$Ru M$"o$ssbauer parameters of ruthenium-nitrosyl complexes

Kaneko, Masashi; Kato, Akane*; Nakashima, Satoru*; Kitatsuji, Yoshihiro

Inorganic Chemistry, 58(20), p.14024 - 14033, 2019/10

 Times Cited Count:1 Percentile:72.9(Chemistry, Inorganic & Nuclear)

We applied density functional theory calculations to ruthenium-nitrosyl complexes, which are known to exist in high-level radioactive waste, to give a theoretical correlation between $$^{99}$$Ru M$"o$ssbauer spectroscopic parameters ($$delta$$ and $$Delta$$$$E_{rm Q}$$) and ligand field strength ($$Delta$$$$_{rm o}$$) for the first time. The structures of the series of complexes, [Ru(NO)L$$_{5}$$] (L = Br$$^{-}$$, Cl$$^{-}$$, NH$$_{3}$$, CN$$^{-}$$), were modeled based on the corresponding single-crystal X-ray coordinates. The comparisons of the geometries and total energies between the different spin states suggested that the singlet spin state of [Ru(II)(NO$$^{+}$$)L$$_{5}$$] complexes were the most stable. The calculated results of both the $$delta$$ and $$Delta$$$$E_{rm Q}$$ values reproduced the experimental results by reported previously and increased in the order of L = Br$$^{-}$$, Cl$$^{-}$$, NH$$_{3}$$, CN$$^{-}$$. Finally, we estimated the ligand field strength ($$Delta$$$$_{rm o}$$) based on molecular orbitals, assuming C$$_{rm 4v}$$ symmetry and showed the increase of $$Delta$$$$_{rm o}$$ values in that order, being consistent with well-known spectrochemical series of ligands. The increase attributes to the strengthening of the abilities of $$sigma$$-donor and $$pi$$-acceptor of the L-ligands to the Ru atom, resulting in the increase of the $$delta$$ values.

Journal Articles

Magnetic field induced triple-$$q$$ magnetic order in trillium lattice antiferromagnet EuPtSi studied by resonant X-ray scattering

Tabata, Chihiro*; Matsumura, Takeshi*; Nakao, Hironori*; Michimura, Shinji*; Kakihana, Masashi*; Inami, Toshiya*; Kaneko, Koji; Hedo, Masato*; Nakama, Takao*; Onuki, Yoshichika*

Journal of the Physical Society of Japan, 88(9), p.093704_1 - 093704_5, 2019/09

 Times Cited Count:4 Percentile:30.92(Physics, Multidisciplinary)

Journal Articles

Unique helical magnetic order and field-induced phase in trillium lattice antiferromagnet EuPtSi

Kaneko, Koji; Frontzek, M. D.*; Matsuda, Masaaki*; Nakao, Akiko*; Munakata, Koji*; Ohara, Takashi; Kakihana, Masashi*; Haga, Yoshinori; Hedo, Masato*; Nakama, Takao*; et al.

Journal of the Physical Society of Japan, 88, p.013702_1 - 013702_5, 2019/01

 Times Cited Count:14 Percentile:4.99(Physics, Multidisciplinary)

Journal Articles

Benchmark study of DFT with Eu and Np M$"o$ssbauer isomer shifts using second-order Douglas-Kroll-Hess Hamiltonian

Kaneko, Masashi; Watanabe, Masayuki; Miyashita, Sunao*; Nakashima, Satoru*

Hyperfine Interactions, 239(1), p.20_1 - 20_10, 2018/12

 Times Cited Count:0 Percentile:100

We optimized a mixing ratio of exchange energy between pure DFT and exact Hartree-Fock using TPSS exchange-correlation functional to estimate the accurate coordination bonds in f-block complexes by numerically benchmarking with the experimental data of M$"o$ssbauer isomer shifts for $$^{151}$$Eu and $$^{237}$$Np nuclides. Second-order Douglas-Kroll-Hess Hamiltonian with segmented all-electron relativistically contracted basis set was employed to calculate the electron densities at Eu and Np nuclei, i.e. contact densities, for each five complexes for Eu(III) and Np(IV) systems. We compared the root mean square deviation values of their isomer shifts between experiment and calculation by changing the mixing ratio of Hartree-Fock exchange parameter from 0 to 100 % at intervals of 10 %. As the result, it was indicated that the mixing ratio of 30 and 60 % for Eu and Np benchmark systems, respectively, gives the smallest deviation values. Mulliken's spin population analysis indicated that the covalency in the metal-ligand bonds for both Eu and Np complexes decreases with increasing the Hartree-Fock exchange admixture.

Journal Articles

On/off spin-crossover phenomenon and control of the transition temperature in assembled Iron(II) complexes

Nakashima, Satoru*; Kaneko, Masashi; Yoshinami, Keisuke*; Iwai, Saki*; Dote, Haruka*

Hyperfine Interactions, 239(1), p.39_1 - 39_15, 2018/12

 Times Cited Count:1 Percentile:31.37

The present study reveals the on/off of spin-crossover (SCO) phenomenon in assembled Fe(II) complexes bridged by bis(pyridyl) type ligand. Whether SCO phenomenon occurs or not in assembled Fe(II) complexes bridged by bis(pyridyl) type ligand is determined by local structure around iron atom. SCO phenomenon occurs when the coordinating pyridines facing to each other across the iron atom are propeller type, while the phenomenon does not occur when they are parallel type or distorted propeller type. DFT calculation explained that, in the shortening of Fe-pyridine bonds when changing from high-spin state to low-spin state, the pyridines of propeller type can approach the iron atom with smaller steric hindrance than those of parallel and distorted propeller type complexes. The local structure is controlled by introducing methyl substituent and introducing $$pi$$-system, changing SCO phenomenon. And the transition temperature of SCO is also controlled in assembled complexes bridged by 1,2-bis(4-pyridyl)ethane by mixing anionic ligand.

Journal Articles

Theoretical elucidation of Am(III)/Cm(III) separation mechanism with diamide-type ligands using relativistic density functional theory calculation

Kaneko, Masashi; Suzuki, Hideya; Matsumura, Tatsuro

Inorganic Chemistry, 57(23), p.14513 - 14523, 2018/12

 Times Cited Count:4 Percentile:49.71(Chemistry, Inorganic & Nuclear)

We elucidated the separation mechanism between Am(III) and Cm(III) ions by using two different types of diamide ligands, diglycolamide (DGA) and alkylated diamide amine (ADAAM), by means of the density functional theory technique and electron density analysis. The molecular geometries and formation reactions of the metal-ligand complexes were modeled by using [M(DGA)$$_{3}$$]$$^{3+}$$ and [M(ADAAM)(NO$$_{3}$$)$$_{3}$$(H$$_{2}$$O)]. We successfully reproduced Cm(III) selectivity over Am(III) with DGA and Am(III) selectivity over Cm(III) with ADAAM. Furthermore, we analyzed the bonding properties between the metal ion and the diamide-type ligands by using model complexes, [M(DGA)$$_{3}$$]$$^{3+}$$ and [M(ADAAM)(NO$$_{3}$$)$$_{3}$$(H$$_{2}$$O)], and revealed the differences in terms of the bond dissociation energy and the metal 5f-orbital participation in the covalency between the Am(III) and the Cm(III) complexes. It was suggested that the differences were key factors to understand the Am(III)/Cm(III) selectivity.

Journal Articles

Computational chemical analysis of Eu(III) and Am(III) complexes with pnictogen-donor ligands using DFT calculations

Kimura, Taiki*; Kaneko, Masashi; Watanabe, Masayuki; Miyashita, Sunao*; Nakashima, Satoru*

Dalton Transactions (Internet), 47(42), p.14924 - 14931, 2018/11

 Times Cited Count:2 Percentile:72.28(Chemistry, Inorganic & Nuclear)

We demonstrated density functional calculations of Eu(III) and Am(III) complexes with pnictogen-donor (X) ligands, CH$$_{3}$$)$$_{2}$$X-CH$$_{2}$$-CH$$_{2}$$-X(CH$$_{3}$$)$$_{2}$$ (X = N, P, As and Sb). We investigated the optimized structures of the cmoplexes and the Gibbs energy differences in the complex formation reactions. Those results indicated that the N- and P-donor ligands have Am(III) ion selectivity over Eu(III) ion, especially, the P-donor ligand showed the highest selectivity. The tendency of the Am(III)/Eu(III) selectivity by the pnictogen-dono ligands was found to be comparable to that of soft acid classification in hard and soft acids and bases rule. Mulliken's spin population analysis indicated that the bonding property between the metal ion and the pnictogen atoms correlated with the Am(III)/Eu(III) selectivity. In particular, the participation of f-orbital electrons of the metal ion in the covalency was indicated to have an important role for the selectivity.

Journal Articles

Variation of half-life and internal-conversion electron energy spectrum between $$^{235m}$$U oxide and fluoride

Shigekawa, Yudai*; Kasamatsu, Yoshitaka*; Yasuda, Yuki*; Kaneko, Masashi; Watanabe, Masayuki; Shinohara, Atsushi*

Physical Review C, 98(1), p.014306_1 - 014306_5, 2018/07

 Times Cited Count:1 Percentile:77.87(Physics, Nuclear)

The nuclear half-life of $$^{235m}$$U has been reported to vary depending on the chemical environment. In this study, both the half-life and the internal-conversion (IC) electron energy spectrum were measured for $$^{235m}$$U with identical chemical environments for the first time. $$^{235m}$$U oxide and fluoride samples were subjected to these measurements, and clear differences in the half-life and the energy spectrum between these samples were observed. The peaks in the energy spectra were identified with the relativistic density functional theory calculation, and the molecular orbital states of the $$^{235m}$$U oxide and fluoride estimated from the energy spectra and the calculation qualitatively explained the difference in the half-lives between the samples.

Journal Articles

Correlation between Am(III)/Eu(III) selectivity and covalency in metal-chalcogen bonds using density functional calculations

Kaneko, Masashi; Watanabe, Masayuki

Journal of Radioanalytical and Nuclear Chemistry, 316(3), p.1129 - 1137, 2018/06

 Times Cited Count:5 Percentile:20.41(Chemistry, Analytical)

We applied density functional theory calculations to Am(III) and Eu(III) complexes with chalcogen-donor ligands of the formula N(EPMe$$_{2}$$)$$_{2}$$$$^{-}$$ (E = O, S, Se, Te). We calculated the equilibrium structures and relative stabilities of the complexes in the complexation reaction. The results indicated that the tendency of the relative stability is O $$ll$$ S $$sim$$ Se $$sim$$ Te, which is consistent with the trend of soft acid classification. Molecular orbital overlap population analysis suggested that this tendency can be correlated with the bonding type in the covalent interaction between the f-orbitals of the metal atom and the chalcogen-donor atoms.

Journal Articles

Estimation of $$Delta$$${it R}$/${it R}$ values by benchmark study of the M$"o$ssbauer Isomer shifts for Ru, Os complexes using relativistic DFT calculations

Kaneko, Masashi; Yasuhara, Hiroki*; Miyashita, Sunao*; Nakashima, Satoru*

Hyperfine Interactions, 238(1), p.36_1 - 36_9, 2017/11


 Times Cited Count:1 Percentile:28.38

We aim to evaluate the validity of density functional calculations to the bonding property for Ru and Os complexes. We performed the benchmarking of theoretical computational method with $$^{99}$$Ru, $$^{189}$$Os M$"o$ssbauer isomer shifts. As the result, the computational values of the electron densities at nucleus position correlated with the experimental M$"o$ssbauer isomer shifts.

Journal Articles

Bonding study on trivalent europium complexes by combining M$"o$ssbauer isomer shifts with density functional calculations

Kaneko, Masashi; Watanabe, Masayuki; Miyashita, Sunao*; Nakashima, Satoru*

Radioisotopes, 66(8), p.289 - 300, 2017/08

Scalar-relativistic density functional calculations applied to some trivalent europium complexes. Five Eu(III) complexes whose $$^{151}$$Eu M$"o$ssbauer isomer shifts vary from -1.8 to 0.5 mm/s are referred by previously reported results. Geometrical optimizations of their complexes reproduces the experimental coordination structures. Single-point calculations are applied to their optimized geometries at three density functionals, namely, BP86, B3LYP, and B2PLYP, to obtain their electron densities at Eu nucleus. A comparison of the linearity between the electron densities and the corresponding $$^{151}$$Eu M$"o$ssbauer isomer shifts reveals that B2PLYP functional shows the best linearity. Electron population and bond analyses indicate that d- and f-orbital electrons of Eu ion in the complexes are found to be correlated to the experimental $$^{151}$$Eu M$"o$ssbauer isomer shifts. This indicates that the d- and f-orbital electrons are involved in the covalent interaction of the coordination bond between the Eu ion and the ligands.

Journal Articles

Bonding study on d- and f-block coordination compounds by combining density functional calculations with M$"o$ssbauer spectroscopic parameters

Kaneko, Masashi

Hosha Kagaku, (35), p.36 - 39, 2017/03

This paper is an article for research introduction by winner of the Japan Society of Nuclear and Radiochemical Sciences Encouragement Price 2016. It was mentioned about the achievements which revealed the spin transition behavior of iron complex and the separation mechanism of actinides from lanthanides.

Journal Articles

Roles of d- and f-orbital electrons in the complexation of Eu(III) and Am(III) ions with alkyldithiophosphinic acid and alkylphosphinic acid using scalar-relativistic DFT calculations

Kaneko, Masashi; Watanabe, Masayuki; Miyashita, Sunao*; Nakashima, Satoru*

Journal of Nuclear and Radiochemical Sciences (Internet), 17, p.9 - 15, 2017/03

Density functional calculations were applied to the complexation of Eu(III) and Am(III) ions with phosphinic acid (O-donor) and dihiophosphinic acid (S-donor) from the viewpoint of the bonding nature of valence orbitals in metal ion. Two and four conformers for S-donor and O-donor complexes, respectively were optimized. Their stabilization energies by complex formation toward [M(H$$_{2}$$O)$$_{9}$$]$$^{3+}$$ were estimated. As the result, the energies reproduced the experimental Am(III)/Eu(III) selectivity that O-donor ligand preferably coordinates to Eu(III) ion, whereas S-donor ligand selectively coordinates to Am(III) ion. Focused on the bonding natures of d and f-orbital electrons, it was indicated that the d-orbital electrons in both Eu and Am complexes participate in the covalency as bonding-type nature and have the almost same contribution. Meanwhile, the contribution of the f-orbital electrons was different between Eu and Am complexes and indicated that in the case of S-donor complex, non-bonding type and bonding type contributions were observed for Eu and Am complexes, respectively and in the case of O-donor complex, bonding type and anti-bonding type contributions were observed for Eu and Am complexes, respectively. This result suggested that the bonding natures of d-orbital electrons contribute to the geometrical similarity of molecular structures for Eu and Am complexes and the bonding natures of f-orbital electrons contribute to the difference in the selectivity of Eu and Am ions.

Journal Articles

A Spin-crossover phenomenon depending on the environment around an iron atom for the assembled coordination polymers

Nakashima, Satoru*; Kaneko, Masashi

Advances in Chemistry Research, Vol.36, p.171 - 195, 2017/01

Spin-crossover (SCO) phenomena of the assembled coordination polymers are introduced. When the bridging ligand is flexible like 1,2-bis(4-pyridyl)ethane, 1,3-bis(4-pyridyl)propane, a variety of assembled structure can be obtained, depending on the conformer of the ligand and the guest molecules. Guest-dependent SCO phenomena of the assembled iron complexes are shown. Density functional theory is applied to know the cause of guest-dependent SCO phenomena. The validity of an iron mono-nucleus model is evaluated for the coordination polymers. It is shown that SCO occurs or not depends on the local structure around iron ion.

Journal Articles

Measurement of atomic radii

Kaneko, Masashi

Gendai Kagaku, (549), P. 11, 2016/12

This article was made to explain the paper stating that atomic size was measured by computational method (R. Hoffmann, et al., Chem. Eur. J., 22, doi: 10.1002/chem.201602949) for student majoring chemistry. The estimation of atomic size was performed by means relativistic density functional theory. The atomic radii of noble gas and d-block elements were discussed.

Journal Articles

The Separation mechanism of Am(III) from Eu(III) by diglycolamide and nitrilotriacetamide extraction reagents using DFT calculations

Kaneko, Masashi; Watanabe, Masayuki; Matsumura, Tatsuro

Dalton Transactions, 45(43), p.17530 - 17537, 2016/11


 Times Cited Count:19 Percentile:13.46(Chemistry, Inorganic & Nuclear)

Relativistic density functional calculations were applied to study the separation behaviors of Am(III) ion from Eu(III) ion by diglycolamide (DGA) and nitrilotriacetamide (NTA) ligands in order to understand the difference in the separation mechanism of their reagents. The complexation reaction was modeled on the basis of previous experimental studies. The calculated energies based on stabilization by complex formation at the ZORA-B2PLYP/SARC level predicted that the DGA reagent preferably coordinated to Eu(III) ion when compared with Am(III) ion. In contrast, the NTA reagent selectively coordinated to Am(III) ion when compared with Eu(III) ion. These results reproduced the experimental selectivity of DGA and NTA ligands toward Eu(III) and Am(III) ions. Mulliken's population analyses implied that the difference in the contribution of the bonding property between the f-orbital of Am and donor atoms determined the comparative stability of Eu and Am complexes.

Journal Articles

Science from the initial operation of HRC

Ito, Shinichi*; Yokoo, Tetsuya*; Masuda, Takatsugu*; Yoshizawa, Hideki*; Soda, Minoru*; Ikeda, Yoichi*; Ibuka, Soshi*; Kawana, Daichi*; Sato, Taku*; Nambu, Yusuke*; et al.

JPS Conference Proceedings (Internet), 8, p.034001_1 - 034001_6, 2015/09

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