Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.cplett.2021.139263

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Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

Small hydrogen inorganic molecules such as water have no positron binding ability. We revealed that their hydrogen bonded binary molecular clusters exhibit greater positron affinities due to the increased dipole moments and polarization effect.

DOI： 10.1039/d2cp03813g

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Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

Decomposition analysis shows that the solvent reorientation effect causes solvatofluorochromism of TTz dyes.

DOI： 10.1039/d2ra06454e

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Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acsomega.1c03409

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

The positronic bound state for the non-polar carbon disulfide (CS2) has been experimentally identified, although previous theoretical investigations, which were dedicated to studying the positronic CS2 monomer, could not reasonably reproduce the experimentally measured positron affinity. In the present study, we performed analysis of the vibrational averaged positron affinity for the positronic CS2 dimer, [C2S4; e(+)], using the Hartree-Fock and configuration interaction levels of the multi-component molecular orbital method combined with the self-consistent field level of the vibrational variational Monte Carlo method. We demonstrated that the equilibrium structure of the non-polar C2S4 can have the positronic bound state with a positron affinity of about 46.18 meV in the configuration interaction level, while this is 0 meV in the Hartree-Fock level. Furthermore, by taking into account the vibrational effect, we succeeded in reproducing the resonant positron kinetic energies lying close to the experimental value, where the vibrational averaged positron affinity becomes greater with an increased dipole moment and dipole polarizability. We also showed possible mechanisms to effectively enhance the resonant positron capture for [C2S4; e(+)], associated with both the infrared active and infrared inactive vibrational modes.

DOI： 10.1039/d1cp02808a

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Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

We found that CS₂ obtains positron binding ability by dimerization with vibrational Feshbach resonance.

DOI： 10.1039/d1cp02808a

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AIP Publishing  

We studied the positron (e+) interaction with the hydrogen molecular dianion H2 2- to form the positronic bound state of [H-; e+; H-] using the first-principles quantum Monte Carlo method combined with the multi-component molecular orbital one. H2 2- itself is unstable, but it was shown that such an unbound H2 2- may become stable by intermediating a positron and forming the positronic covalent bond of the [H-; e+; H-] system [J. Charry et al., Angew. Chem., Int. Ed. 57, 8859-8864 (2018)]. We newly found that [H-; e+; H-] has double minima containing another positronic bound state of [H2; Ps-]-like configuration with the positronium negative ion Ps- at the bond distance approximately equal to the equilibrium H2 molecule. Our multi-component variational Monte Carlo calculation and the multi-component configuration interaction one resulted in the positronic covalent bonded structure being the global minimum, whereas a more sophisticated multi-component diffusion Monte Carlo calculation clearly showed that the [H2; Ps-]-like structure at the short bond distance is energetically more stable than the positronic covalent bonded one. The relaxation due to interparticle correlation effects pertinent to Ps- (or Ps) formation is crucial for the formation of the Ps-A2-like structure for binding a positron to the non-polar negatively charged dihydrogen.

DOI： 10.1063/5.0022673

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Publishing type：Research paper (international conference proceedings)  

Synopsis We theoretically analyzed the positron affinity (PA) of acetaldehyde molecule at several vibrational excited states toward the elucidation of physical and chemical origin of H/D isotope shift in the molecular PA value. We found that (i) the acetaldehyde molecule has different PA values and its H/D isotope shift for each vibrational state, and (ii) H/D isotope shift in the PA values at vibrational excited states are mainly due to the change in the dipole moment by the vibrational excitations.

DOI： 10.1088/1742-6596/1412/22/222012

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Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

DOI： 10.1140/epjd/e2020-100538-3

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Other Link： http://link.springer.com/article/10.1140/epjd/e2020-100538-3/fulltext.html

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

DOI： 10.1140/epjd/e2019-100147-y

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Other Link： http://link.springer.com/article/10.1140/epjd/e2019-100147-y/fulltext.html

Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acs.jpca.8b11653

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.comptc.2018.11.013

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier B.V.  

We theoretically discuss the dynamics of the chemical reaction process induced by positron attachment, e+ + LiH → Li+ + [H−
e+]. Simple model pseudopotentials were developed on the basis of the electrostatic interaction between e+ and LiH with a large dipole moment, where some numerical parameters were chosen to qualitatively reproduce the previous-reported ab initio positron-bound adiabatic potential energy curve of [LiH
e+]. Using the developed pseudopotential models, we have performed time-independent quantum scattering calculations using the hyperspherical coordinate. Although the main scattering processes of the e+ + LiH collision are rotational and vibrational excitation processes, it is found that the calculated probabilities for the dissociative positron attachment (DPA) process are not very small within the present pseudopotential framework. This suggest that the DPA process to LiH can be observed in the future experiments.

DOI： 10.1016/j.comptc.2017.11.023

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1002/jcc.25387

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We present computational results of vibrationally enhanced positron annihilation in the e(+) + HCN/DCN collisions within a local complex potential model. Vibrationally elastic and inelastic cross sections and effective annihilation rates were calculated by solving a time-dependent complex-potential Schrodinger equation under the ab initio potential energy surface for the positron attached HCN molecule, [HCN; e(+)], with multi-component configuration interaction level (Kita and Tachikawa, 2014). We discuss the effect of vibrational excitation on the positron affinities from the obtained vibrational resonance features. (c) 2017 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.cplett.2017.03.025

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IOP PUBLISHING LTD  

We theoretically analyzed the effect of the anharmonicity and the inter-mode couplings of molecular vibrations on a positron affinity (PA), which is the binding energy of a positron, of HCN and CH2O molecules. Based on the different theoretical approaches for describing vibrational wave functions, we confirmed that (i) not only the anharmonicity but also the inter-mode couplings on potential energy surface are indispensable for the accurate calculation of PA values, and (ii) the effect of inter-mode couplings on a positron affinity surface is sufficiently weaker than that on potential energy surface.

DOI： 10.1088/1742-6596/791/1/012015

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

We theoretically analyzed a positron affinity (PA), which is the binding energy of a positron, of the non-polar carbon disulfide (CS2) molecule at vibrational excited states to elucidate the effect of molecular vibrations on the binding of positron to the molecule. Using the configuration interaction method of the multi-component molecular orbital theory and anharmonic vibrational state analysis with vibrational quantum Monte Carlo technique, the vibrational averaged PA values are calculated as 0.39, 2.03, and 5.02 meV for the ground state, fundamental tone, and overtone states of asymmetric stretching mode, respectively. The PA value of CS2 molecule is found to be enhanced by the vibrational excitation of only asymmetric stretching mode compared to the value at the vibrational ground state. With the linear regression analysis, we have confirmed that such enhancement of vibrational averaged PA values mainly arises from the increment of molecular permanent dipole moment due to the vibrational excitations of the asymmetric stretching mode.

DOI： 10.1140/epjd/e2016-70140-7

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER CHEMICAL SOC  

Positron affinities (PAs), which is the binding energy of a positron, of hydrogen cyanide (HCN) and formaldehyde (CH2O) molecules at vibrational excited states were theoretically analyzed with both the multi-component molecular orbital and vibrational quantum Monte Carlo methods, in order to elucidate the effect of molecular vibrations on the binding of a positron to the molecules. For HCN molecule, we found that the vibrational excitations of the CN and CH stretching modes enhance PA values in comparison to the value at the ground state, whereas the excitation of bending mode deenhances it. For CH2O molecule, the vibrational excitation of C=0 stretching mode gives the largest contribution to the PA enhancement among all vibrational modes. Using the linear regression analysis, we confirmed that the PA variations at each vibrational state mainly arise from the changes in the permanent dipole moment by vibrational excitations.

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Publishing type：Research paper (scientific journal)   Publisher：Society of Computer Chemistry Japan  

DOI： 10.2477/jccj.2016-0016

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

DOI： 10.11316/jpsgaiyo.71.1.0_799

CiNii Books

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

DOI： 10.11316/jpsgaiyo.71.1.0_711

CiNii Books

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

The magnetic coupling of the chromium dimer cation, Cr-2(+), has been an outstanding problem for decades. An optical absorption spectrum of Cr-2(+) has been obtained by photodissociation spectroscopy in the photon-energy range from 2.0 to 5.0 eV. Besides, calculations have been performed by the equation-of-motion coupled-cluster singles and doubles method for vertical excitation of the species. Their coincidence supports our assignment that the ground electronic state exhibits a ferromagnetic spin coupling, which is contrary to those of neutral and negatively charged dimers, Cr-2 and Cr-2(-), in their lowest spin states. (C) 2015 AIP Publishing LLC.

DOI： 10.1063/1.4907197

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

The vertical positron affinity (PA) value at the equilibrium position of a formaldehyde molecule is predicted as +25(3) meV with the highly accurate quantum Monte Carlo method. Applying anharmonic vibrational analysis, we have found that the vibrational excitation of the C = O stretching mode drastically enhances the PA value, due to the increment of the molecular dipole moment along this mode. Our predictions of the vibrational averaged PA values at the fundamental and overtone states are 31 and 36 meV, respectively, which strongly supports the conclusion that a positron can bind to formaldehyde.

DOI： 10.1103/PhysRevA.89.062711

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

We theoretically analyzed positron affinities (PA) of hydrogen cyanide (HCN) molecule at vibrational excited states to elucidate the effect of molecular vibrations on the binding of a positron to the molecule. Using the configuration interaction method in the multi-component molecular orbital theory and anharmonic vibrational state analysis with the variational Monte Carlo technique, we found that the vibrational excitations of the CN and CH stretching modes enhance the PA value compared to that of the vibrational ground state, whereas the excitation of bending mode deenhances it. The largest PA enhancement is found at the excited states of the CH stretching mode; the PA values are 43.02 (1) and 46.34 (2) meV for the fundamental tone and overtone states, respectively. With the linear regression analysis, we confirmed that the PA variation of HCN molecule at each vibrational state arises from the variation of permanent dipole moment and dipole-polarizability due to each vibrational excitation.

DOI： 10.1140/epjd/e2014-40799-9

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

Energy thresholds for dissociation channels of positronic alkali-metal hydrides, [XH;e(+)] (X = Li, Na, and K), to XH + e(+)(positron dissociation), XH+ + Ps (positronium dissociation), and X+ + [H-;e(+)] (positronic hydride ion dissociation) have been calculated using quantum Monte Carlo and high-level ab initio molecular orbital methods, and including quantum zero-point vibrational energy of all of the particles. As the atomic number of X increases from Li to K, the dissociation energy to XH + e(+) increases because the dipole moment of XH increases with the atomic number of X, while the dissociation energy to XH+ + Ps decreases. The energy threshold for the ionic dissociation to X+ + [H-;e(+)] is also reduced, and we obtain 0.975 (3) eV, 0.573 (12) eV, and 0.472 (19) eV for [LiH;e(+)], [NaH;e(+)], and [KH;e(+)], respectively, for this channel. Our results strongly support the conclusion that, among these three channels, the lowest energy dissociation for [XH;e(+)] is the pathway to X+ + [H-;e(+)], where X = Li, Na, and K.

DOI： 10.1140/epjd/e2014-40734-2

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Language：English   Publisher：WILEY-BLACKWELL  

DOI： 10.1002/qua.24541

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PHYSICAL SOC REPUBLIC CHINA  

In order to elucidate the element specificity of the S parameters of polymers containing C, O, or F atoms reported by Sato et a l. with the Doppler broadening of positron annihilation radiation measurement [K. Sato, et a l., Phys. Rev. B 71, 012201, (2005).], we theoretically analyzed the molecular orbitals of small size of the polymer molecules with an ab initio molecular orbital method. With a linear regression analysis, we found a strong correlation between the average kinetic energies of the valence electrons and the contribution of a free positron to the experimental S parameters for the C-, O-, and F-groups. As with a consideration of the kinetic energies of the valence electrons and the electronegativity of the C, O, and F atoms, we conclude that the element specificity of the experimental S parameters for each of the C-, O-, and F-groups is roughly explained by a difference in the electronegativity of the C, O, and F atoms.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PHYSICAL SOC REPUBLIC CHINA  

We performed ab initio molecular orbital and density functional theory calculations for enhanced cyan fluorescent protein, gold fluorescent protein, and (4-Me)-tryptophan enhanced cyan fluorescent protein to elucidate the substituent effect on the electronic structure of the chromophore in the fluorescent proteins. The electron correlation effect on the electronic structures is investigated as well. Our calculated excitation and deexcitation energies reasonably reproduce the corresponding experimental values. The qualitative Stokes shifts for the three fluorescent proteins were realized taking the electronic correlation into account. We found that the amino group of the chromophore in gold fluorescent protein enhances charge transfer among the ground and excited states, while the substituent effect of the methyl group, which is a weak electron donor, in (4-Me)-tryptophan enhanced cyan fluorescent protein was small. The charge transfer is the origin of the Stokes shift found in gold fluorescent protein. Thus, we succeeded in elucidating the substituent effect on the electronic structure of the chromophore in three fluorescent proteins.

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Hole attack: A theoretical one-electron oxidation of nucleic base molecules and their pairs by positron is proposed, based on the calculations for positron-attached neutral forms of species, adenine (A), thymine (T), guanine (G), cytosine (C), and their Watson-Crick base pairs (A-T and G-C). The results reveal that binding of a positron to neutral isolated nucleic base molecules is base-selective. © 2013 WILEY-VCH Verlag GmbH &amp
Co. KGaA, Weinheim.

DOI： 10.1002/cphc.201300549

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

Molecular dynamics simulations of hexameric molecular capsules constructed from gear-shaped amphiphile molecules with the aid of solvophobic effect and van der Waals force were performed with general AMBER force field to elucidate the thermodynamical properties of the capsules. The optimized structure of the capsule 16 consisting of methylated gear-shaped molecules (1) is a nearly cubic structure, whereas the distorted structure is found for the capsule 26 consisting of ones lacking three methyl groups, (2) so as to maximize the contact surface. Disassembly temperature for the demethylated capsule 26, similar to 210 K, is much lower than that for the methylated one 16, similar to 340 K, which is consistent with the corresponding experimental result that 16 is stable, whereas 2 exists as a monomer in aqueous methanol. (C) 2012 Wiley Periodicals, Inc.

DOI： 10.1002/qua.24108

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY  

To demonstrate the binding of a positron to nonpolar CX2 (X = O and S) molecules, we have estimated the vibrational averaged positron affinity (PA) values for the harmonic asymmetric stretching vibrational coordinate with the multi-component molecular orbital method. A positron can be attached at higher vibrational excitation levels, and vibrational averaged PA values become greater as the number of vibrational quantum number increases. The resultant PA values of carbon disulfide (CS2) molecule are greater than those of CO2, which is consistent with the corresponding property such as infrared (IR) intensity and polarizability of the parent species. (c) 2012 Wiley Periodicals, Inc.

DOI： 10.1002/qua.24111

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We have first performed 'gold-standard' CCSD(T) calculations of the chromium dimer cation using a cc-pVQZ basis set in order to elucidate its electronic structures, especially for identification of its ground-state term. Our CCSD(T)/cc-pVQZ calculations have predicted that it is the highest-spin state, in contrast to a previous speculation of the lowest-spin state by density functional theory with semi-local functionals. The ground-state binding energy is found to be 1.49 eV, which reasonably agrees with the corresponding experimental value of 1.30 +/- 0.06 eV. We have also provided several spectroscopic constants for references in future theoretical and experimental works. (C) 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.cplett.2012.11.017

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier B.V.  

To theoretically analyze the nuclear quantum effects of protons on two hydrogen bonds around the chromophore (CRO) in the photoactive yellow protein (PYP), we have calculated simple cluster model consisting of CRO, Glu46, and Tyr42 residues in PYP with the multi-component molecular orbital method and multi-component density functional theory, which can take account of quantum fluctuations of light mass particles. The average OO distances between CRO and Glu46 and between CRO and Tyr42 with our methods are shorter than the corresponding equilibrium ones, while the OH distances become longer due to the anharmonicity of the potential. The H/D geometrical isotope effect is also found, that is, the distances between oxygen atoms are elongated by the deuterium substitution, known as Ubbelohde effect. © 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.chemphys.2012.11.022

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

To theoretically demonstrate the binding of a positron to a nonpolar or small dipole molecule, we have calculated the vibrational averaged positron affinity (PA) values along the harmonic asymmetric stretching vibrational coordinate with the configuration interaction level of multi-component molecular orbital method for CXY (X, Y = O, S, and Se) molecules. For CSe2 and CSSe molecules, a positron can even be attached at the equilibrium structures, due to the effect of the induced dipole moment with large polarizability values. For a CS2 molecule, the positive PA value is obtained at the lowest vibrational excited state in our scheme. Although there is no direct experimental evidence for the positron-binding to CO2, COS, and COSe molecules, we have predicted positron-binding for these molecules at higher vibrational excited states.

DOI： 10.1039/c3cp52572d

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

The feature of positron binding to twenty neutral amino acid molecules with the global minimum (GM) and intramoleculear hydrogen-bonded (HB) structures was analysed using the ab initio multicomponent molecular orbital method. All amino acid molecules in the intramoleculear HB structures have positive positron affinity (PA, the binding energy of a positron) values, which means that a positron can be attached to parent molecules, while in the GM structures only three amino acid molecules of Gln, Trp, and His have positive PA values. Analysing the positronic orbitals of each positronic amino acid molecule and the electrostatic potential maps of the corresponding parent molecules, we found that long-range electrostatic interaction is the most crucial role in positron binding to neutral amino acid molecules. The strong correlation is observed between the PA and dipole moment, that is, a polar molecule with a large dipole moment has a large PA value. The critical dipole moment of neutral amino acid molecules for binding a positron was found at about 3.46 Debye. From the systematic analysis of twenty kinds of amino acid molecule, we theoretically confirmed the possibility of positron binding to conformers of amino acid molecules with strong dipole moment.

DOI： 10.1140/epjd/e2012-20638-y

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

Characteristic features of the positron-binding structure of some carbonyl and aldehyde species such as formaldehyde, acetaldehyde, acetone and propionaldehyde are discussed with the configuration interaction scheme of multi-component molecular orbital (MC_MO) calculations. This method can take the electron-positron correlation contribution into account through single electronic-single positronic excitation configurations. Our vertical positron affinity (PA) values of acetaldehyde and acetone with electronic 6-31++G(2df,2pd) and positronic [15s15p3d2f1g] basis sets are as 52 and 92 meV, which can be compared to the recent experimental values of 90 and 173 meV by Danielson et al (2010 Phys. Rev. Lett. 104 233201). For formaldehyde we have also found that the PA values are enhanced by including the local C=O vibrational contribution from the vertical PA value of 15 meV to 17, 21 and 25 meV after averaging over the zeroth, first and second vibrational states, respectively, due to the anharmonicity of the potential.

DOI： 10.1088/1367-2630/14/3/035004

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER CHEMICAL SOC  

We report the theoretical investigations of the positron binding to alkali-metal hydrides (LiH, NaH, and KH) and hydrogen cyanide molecule (HCN) using quantum Monte Carlo (QMC) methods. We have obtained the lowest variational energies of positron-attached NaH, KH, and HCN systems so far, and larger positron affinities of these molecules than the theoretical predictions by previous configuration interaction calculations. Our study also confirms the strong correlation between the positron affinity and dipole moment of alkali-metal hydrides and the binding of a positron in the electrostatic field of the HCN molecule. In this report, we have described our methodology for analyzing a positron-attached molecule (positronic compound) using QMC techniques, and have reviewed our recent results of QMC calculations of the positron binding to these polar molecules.

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Ab initio molecular orbital and density functional theory calculations with inclusion of dispersion interaction effect are employed to reveal the characteristic features of intermolecular interactions for the molecular capsule (1 (6)) consisting of six gear-shaped amphiphile molecules (1) discovered by Hiraoka et al. (J Am Chem Soc 130:14368-14369, 2008). The contributions of CH-pi and pi-pi type dispersion energies are found to be indispensable for the formation of hexameric capsule 1 (6) by the analysis of decomposed interaction energies between fragmented-model species in the 1 molecule. We have also calculated the hexameric capsule (2 (6)) from demethylated 1 molecule (2). Such subtle structural difference induces the different characters of intermolecular interactions, in which the stabilization energy of hexameric 2 (6) capsule is about 40 kcal/mol smaller than that of the original 1 (6) capsule, due to the lack of three methyl groups for the CH-pi interactions in 2 molecules.

DOI： 10.1007/s00214-011-1053-2

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We applied the multi-component density functional theory (MC_DFT) combined with the gauge - including atomic orbital (GIAO) and continuous set of gauge transformation (CSGT) techniques to some small molecules (H-2, HD, H2O, CH4, etc.) for analyzing the nuclear quantum effect on molecular magnetic properties, such as nuclear magnetic shielding constant and molecular magnetic susceptibility. Our method clearly shows that the absolute isotropic magnetic shielding constant depends on the spatial distribution of quantum nuclei, that is, the deuteron-isotopomers have the weaker deshielding effect than the proton-isotopomers. We also found the magnetic isotope effect with respect to the molecular magnetic susceptibility, that is, the magnetic susceptibility of the deuteron-isotopomers is smaller than that of the proton-isotopomers. (C) 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.comptc.2011.03.009

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

Quantum Monte Carlo methods are used to investigate the binding of a positron to the alkali-metal hydrides, XH (X = Na and K). We obtain positron affinities for the NaH and KH molecules of 1.422(10) eV and 2.051(39) eV, respectively. These are considerably larger than the previous results of 1.035 eV and 1.273 eV obtained from multireference single- and double-excitation configuration interaction calculations. Together with our previous results for [LiH;e(+)] [Y. Kita , J. Chem. Phys. 131, 134310 (2009)], our study confirms the strong correlation between the positron affinity and dipole moment of alkali-metal hydrides. (C) 2011 American Institute of Physics. [doi:10.1063/1.3620151]

DOI： 10.1063/1.3620151

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

To elucidate the irreversible photoreaction of green fluorescent protein (GFP), we have theoretically analyzed hydrogen-bonding networks and distributions of water molecules around a chromophore (CRO) of GFP before and after photoactivation. Our molecular dynamics simulation clearly shows that such irreversibility arises from the migration of water molecules to the hollowed out region due to the reorientation of amino acid residues together with the disappearance of hydrogen-bonding networks around the CRO.

DOI： 10.1246/cl.2011.476

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Characteristic features of the positron binding structure of some nitrile (-CN functional group) species such as acetonitrile, cyanoacetylene, acrylonitrile, and propionitrile are discussed with the configuration interaction scheme of multi-component molecular orbital calculations. This method can take the electron-positron correlation contribution into account through single electronic-single positronic excitation configurations. Our PA value of acetonitrile with the electronic 6-31 + + G(2df,2pd) and positronic [15s15p3d2f1g] basis set is calculated as 4.96 mhartree, which agrees to within 25% with the recent experimental value of 6.6 mhartree by Danielson et al. [Phys. Rev. Lett., 2010, 104, 233201]. Our PA values of acrylonitrile and propionitrile (5.70 and 6.04 mhartree) are the largest among these species, which is consistent with the relatively large dipole moments of the latter two systems.

DOI： 10.1039/c0cp01650k

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELSEVIER SCIENCE BV  

We propose a new scheme of the photoactivation and the photobleaching for Dronpa with molecular dynamics method and density functional theory. These processes can be explained by considering cis-trans isomerization in neutral state of chromophore. The proton transfer from anionic to neutral chromophore makes cis-trans isomerization possible via hula-twist rotation process, since the space for cis-trans isomerization is opened at around the region near chromophore by moving out of the imidazole ring on H193 from the position below the phenol ring on chromophore. Then the cis-trans isomerization can occur through the hula-twist process. The contributions from the protein environment around CRO, especially S142 and H193, are indispensable for photoconversion of Dronpa.

DOI： 10.1016/j.procs.2011.04.027

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A variational Monte Carlo study using inhomogencous backflow transformations is reported for the [H-,e(+)] and [Li-,e(+)] positronic compounds The backflow transformations greatly Improve the total energies, positron affinities, and two-photon annihilation rates The Slater-Jastrow-backflow trial wave function is well suited to the theoretical analysis of positronic compounds

DOI： 10.1246/cl.2010.1136

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Transmission electron microscopy (TEM) technique was used to investigate the structure of carbon nanowalls (CNWs). The TEM observation clearly indicated the existence of the bended graphene structure in boundary regions between the crystallites of CNWs. According to this TEM result, the first-principles calculation was employed for the bended coronene molecule as the model of the boundary region between the crystallites of CNWs, to elucidate the mechanism of the hydrogen adsorption to CNWs. The hydrogen adsorption energies onto both on-top and hollow sites become greater as the bending angle increases, because the electronic structure of the carbon atom at the adsorption site changes from sp(2) to sp(3) hybridization character by natural bond orbital analysis. Our computational result is reasonably consistent with the specific feature of hydrogen adsorption to CNWs, which had been reported in our previous work by ultraviolet photoelectron spectroscopy and temperature program desorption measurements by Kinoshita et al.[Chem. Phys. Lett. 450, 360 (2008)]. (C) 2010 American Institute of Physics. [doi:10.1063/1.3446830]

DOI： 10.1063/1.3446830

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DOI： 10.1016/j.bpc.2010.01.008

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Language：English   Publisher：The Biophysical Society of Japan General Incorporated Association  

DOI： 10.2142/biophys.50.S33_5

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Characteristic features of the positron binding properties for F-(H2O)(n) and Cl-(H2O)(n) (n = 0-3) clusters are elucidated by implementation of the energy gradient of the positron-attached complexes with respect to the nuclear coordinates and positronic basis centers in the scheme of the multi-component molecular orbital calculation. The differences in the positron affinities (PAs) between these clusters are found to decrease with the number of water molecules from n = 0 (1.10 eV) to 3 (0.14 and 0.22 eV for vertical and relaxed PAs, respectively), which is consistent with the changes in the hydrogen-bonded distances, the population on halogen atoms, and the characters of positronic orbitals and electronic HOMOs. (C) 2009 Elsevier B. V. All rights reserved.

DOI： 10.1016/j.cplett.2009.09.108

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

Quantum Monte Carlo methods are used to investigate the binding of a positron to the hydrogen cyanide (HCN) and lithium hydride (LiH) molecules. Our value of the adiabatic positron affinity (PA) of LiH of 1.010(3) eV is very close to the best theoretical value of 1.005 eV, obtained from variational calculations using explicitly correlated Gaussian basis sets [K. Strasburger, J. Chem. Phys. 114, 00615 (2001)]. We have obtained a reliable estimate of 0.0378(48) eV for the PA of the HCN molecule, which is almost 20 times larger than that obtained at the Hartree-Fock level, and strongly supports the binding of a positron in the electrostatic field of the HCN molecule. Our results show the importance of correlation effects for describing weakly bound positronic molecular complexes. (C) 2009 American Institute of Physics. [doi:10.1063/1.3239502]

DOI： 10.1063/1.3239502

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PubMed

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We have proposed the computational method to analyze the nuclear quantum effect on the molecular magnetic properties and applied to some small molecules. Our method is based on the multi-component molecular orbital (MC-MO) procedure with the gauge-including atomic orbital (GIAO) and continuous set of gauge transformation (CSGT) methods. The absolute magnetic shielding constants and the magnetic susceptibility are evaluated by the Hartree-Fock level of calculations. Our results show that the deuterons have the weaker deshielding effect than the protons, and the magnetic susceptibility of the deuteron-isotopomer is smaller than that of the proton-isotopomer. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.

DOI： 10.1016/j.theochem.2009.01.035

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Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2477/jccj.H2118M

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Chemical Society of Japan  

We have theoretically analyzed the nuclear quantum effect on the nuclear magnetic shielding (σ) and molecular magnetic susceptibility (χ) of H<SUB>3</SUB>O<SUB>2</SUB><SUP>−</SUP> and N<SUB>2</SUB>H<SUB>7</SUB><SUP>+</SUP> systems with a new implementation combined with the multicomponent density functional theory and the gauge-including atomic orbital or continuous set of gauge transformation techniques. Our method easily reproduces the "deshielding" effect of σ on hydrogen atoms and clearly indicates the existence of the H/D isotope effect on χ in H<SUB>3</SUB>O<SUB>2</SUB><SUP>−</SUP> and N<SUB>2</SUB>H<SUB>7</SUB><SUP>+</SUP> systems.

DOI： 10.1246/cl.2009.1156

CiNii Books

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

We developed the new intermolecular interaction model of C-60 with the quantitative accuracy for the molecular orientational properties in crystals. The energy difference (Delta E) and the activation barrier (E-barrier) between the two stable orientations (P and H orientations) in crystals are in the values of +14.7 and +260 meV in our model, respectively; these values are in fairly good agreement with the experimental values (Delta E similar or equal to+11 meV, E-barrier=+235-+290 meV in experiments). The relaxation calculation for C-60 crystals using our model revealed that there is the reversal of the stable orientations between the P and H orientations under the high H-orientation occupancy (p(H)) in crystals, when p(H &gt;)0.83, Delta E &lt; 0. From the molecular dynamics calculations for C-60 crystals using our model, it is found that the phase transition is induced at T-C=200-260 K, which is consistent with the experimental value of 260 K. Immediately below T-C, we found a great variety of molecular rotational jumps involving that between the P and H orientations every about 10(-9) s due to the thermal activation. In the high temperature phase (&gt; T-C), all molecules rotate irregularly like in Brownian motion involving the rotational "slumber" for similar or equal to 10(-12)-10(-11) s. (c) 2006 American Institute of Physics.

DOI： 10.1063/1.2215601

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WORLD SCIENTIFIC PUBL CO PTE LTD  

We have performed the ab initio molecular orbital calculations for combinations of the fullerene-fragments as the models of the nonbonding interaction of C-60 dimer at the preferred configurations in the simple cubic phase. The intermolecular interaction potentials have been calculated using several basis sets with MP2 level of the electron correlation energy and the basis set superposition error correction. The strong dispersion attractions that is dominant in the van der Waals interaction has been found for the combinations of the fullerene-fragments. The equilibrium intermolecular distances obtained are in good agreement with the corresponding experimental value. The repulsive region of the intermolecular interaction calculated by ab initio method is found to be express by an atom-atom interaction potential with an anisotropic exponential type repulsive term, which is less steep than the conventional Lennard-Jones type potential.

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Language：Japanese   Publisher：Society of Computer Chemistry, Japan  

We have developed quantum multi-component <i>ab initio</i> methods, such as multi-component molecular orbital and multi-component quantum Monte Calro methods, for theoretical calculation of positronic compounds. We have carried out the accurate calculation of positron affinity (PA) and pair annihilation rate for positronic compounds by using these multi-component methods, and found that these values are in reasonable agreement with the corresponding experimental ones. We found that (i) the positronic orbital is much more delocalized than the electronic highest occupied molecular orbital, and (ii) there exist the strong correlation between PA and dipole moment.

DOI： 10.2477/jccj.2013-0019

J-GLOBAL

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Language：Japanese  

J-GLOBAL

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Language：Japanese  

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Language：Japanese  

DOI： 10.15015/00000338

CiNii Books

J-GLOBAL

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Language：Japanese  

CiNii Books

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

CiNii Books

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

CiNii Books

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

CiNii Books

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

CiNii Books

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Language：Japanese   Publisher：一般社団法人日本物理学会  

CiNii Books

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

CiNii Books

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

CiNii Books

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

CiNii Books

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Language：English   Presentation type：Oral presentation (invited, special)  

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Language：English   Presentation type：Oral presentation (invited, special)  

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Language：English   Presentation type：Oral presentation (invited, special)  

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