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

Because deuterium atoms have a higher activation free energy, they cannot move between the stable structures, whereas hydrogen atoms can move freely due to strong nuclear quantum effects.

DOI： 10.1039/d5cp02885j

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Publishing type：Research paper (scientific journal)  

DOI： 10.1063/5.0276067

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

Path integral molecular dynamics simulations were employed to investigate intramolecular hydrogen bonds in biuret analogues. The results indicate that the structural fluctuations originate from the quantum effects of the heavy nuclei in the backbone.

DOI： 10.1039/d5cp02587g

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Authorship：Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：AIP Publishing  

Several N-heterocyclic carbenes (NHCs) are experimentally observed upon the addition of muonium (Mu), and the hyperfine coupling constants (HFCCs) of muon are measured. Theoretical investigation of Mu has been challenging due to significant quantum effects. Herein, we performed an ab initio path integral molecular dynamics (PIMD) simulation, which accurately considers multi-dimensional quantum effects, to theoretically investigate muoniated 1,3-dihydro-2H-imidazole-2-ylidene (Mu-IY). Our findings indicate that quantum effects have two contradictory contributions: the quantum effect of bond vibrations increases the HFCC values, whereas that of out-of-plane angular vibrations decreases the HFCC values. Moreover, we show that the HFCC values of other NHCs can be predicted without the PIMD simulations by applying the structural changes caused by the quantum effect derived from the PIMD simulations of Mu-IY.

DOI： 10.1063/5.0234050

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Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

DOI： 10.1109/jeds.2024.3472062

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

DOI： 10.2477/jccjie.2023-0045

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Publishing type：Research paper (scientific journal)   Publisher：American Physical Society (APS)  

DOI： 10.1103/physrevb.110.104104

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Other Link： http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevB.110.104104/fulltext

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

Path integral molecular dynamics simulations were used to investigate intramolecular hydrogen bonds in biuret and biguanide. Results indicate that π-electrons in the framework are delocalized, regardless of the ease of intramolecular proton transfer.

DOI： 10.1039/d4cp02047b

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Authorship：Lead author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：AIP Publishing  

The theoretical modeling of high-pressure ice remains challenging owing to the complexity in accurately reflecting its properties attributable to nuclear quantum effects. To explore the nuclear quantum effects of the phase transition between Ice VII and Ice X, we introduce an approach based on ab initio path-integral molecular dynamics. The results indicate that quantum effects facilitate the phase transition, with the observed isotope effects consistent with the experimental outcomes. We demonstrate that quantum effects manifest differently across ice phases: In Ice VII, quantum effects reduce the pressure through the centralization of protons. In contrast, in Ice X, quantum effects increase the pressure owing to the increased kinetic energy of zero-point vibration.

DOI： 10.1063/5.0205529

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

DOI： 10.1021/acs.jpca.4c00239

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

A path integral molecular dynamics simulation was employed to investigate the aromaticity of benzene. The results indicated that nuclear quantum fluctuations influence bond distances, reducing aromaticity due to changes in specific vibrational modes.

DOI： 10.1039/d4cp01331j

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

A positive Mu is a useful tool for investigating the spin density of radical species. The theoretical estimation of its behavior in a molecule requires the inclusion of a quantum effect due to the small mass of muonium. Herein, we performed ab initio a path integral molecular dynamics (PIMD) simulation, which accurately included a multi-dimensional quantum effect, for muoniated 9H-xanthene-9-thione (μXT). Our results showed that the quantum effect significantly increased the hyperfine coupling constant (HFCC) value of μXT, which qualitatively improved the calculated HFCC value, compared to the experimental one. In the PIMD simulation, the bond length between muonium and sulfur in μXT is longer than that between hydrogen and sulfur in a hydrogenated 9H-xanthene-9-thione (HXT), leading to a spin density transfer from XT (9H-xanthene-9-thione) to muonium due to neutral dissociations. Additionally, we found that the S-Mu bond in μXT prefers a structure perpendicular to the molecular plane, where the interaction between Mu and the singly occupied molecular orbital of μXT is the strongest. These structural changes resulted in a larger HFCC value in the PIMD simulation of μXT.

DOI： 10.1063/5.0159207

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

Curcumin and its derivatives possess intramolecular low-barrier hydrogen bonds for intramolecular proton transfer. The π-delocalization in the OCCCO framework of the hydrogen bond in these compounds is reorganized concomitantly with the proton transfer. To characterize the hydrogen bond and π-delocalization, we performed path integral molecular dynamics simulations, revealing that although the proton migration and reorganization of the π-delocalized structure showed a positive correlation, the correlation was weak.

DOI： 10.1039/d3cp01821k

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

DOI： 10.1246/bcsj.20230081

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

Path integral molecular dynamics (PIMD) simulations for C6H6, C6D6, and C6T6 have been carried out to directly estimate the distribution of projected C-H(D,T) bond lengths onto the principal axis plane. The average values of raw C-H(D,T) bond lengths obtained from PIMD simulations are in the order of ⟨RC-H⟩ > ⟨RC-D⟩ > ⟨RC-T⟩ due to the anharmonicity of the potential energy curve. However, the projected C-H(D,T) bond lengths are almost the same as those reported by Hirano et al. [J. Mol. Struct. 2021, 1243, 130537]. Our PIMD simulations directly and strongly support the explanation by Hirano et al. for the experimental observations that almost the same projected C-H(D) bond lengths are found for C6H6 and C6D6. The PIMD simulations also predicted the same projected bond lengths for C6T6 as those of C6H(D)6. In addition to the previous local mode analysis, the present PIMD simulations predicted, for benzene isotopologues, that the vibrationally averaged structure is planar but non-flat.

DOI： 10.1021/acs.jpca.2c07197

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

The nuclear quantum effects (NQEs) in dihydrogen bond (DHB) complexes, i.e., NH4+⋯BeH2 and NH4+⋯MgH2, have been investigated using multicomponent quantum mechanics (MC_QM) calculations and path integral molecular dynamics (PIMD) simulation. The MC_QM method considers the NQEs, whereas PIMD considers both the NQEs and the thermal effects. The linear C3v structure is maintained in the optimized structures obtained by the static MP2 and MC_MP2 calculations, whereas the average structures obtained by the PIMD simulation are nonlinear. The strong DHB interaction in NH4+⋯MgH2 suppresses the fluctuation in the Hδ+NMg and Hδ-MgN angles, and hence, the NH4+ rotation did not occur in the simulation of NH4+⋯MgH2. The analysis of the radius of gyration revealed that the nuclear quantum fluctuation in the perpendicular direction is suppressed by the formation of the DHB complex, whereas that in the parallel direction is slightly enhanced in both the Hδ+ and Hδ- nuclei.

DOI： 10.1039/d2cp01999j

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Publishing type：Research paper (scientific journal)  

DOI： 10.1021/acsomega.2c00857

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

DOI： 10.1016/j.comptc.2021.113542

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier {BV}  

DOI： 10.1016/j.chemphys.2021.111381

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s00601-021-01689-y

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

DOI： 10.1002/adfm.202100009

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1246/bcsj.20200120

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Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2477/jccj.2019-0002

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1002/cphc.201701346

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1103/PhysRevLett.115.133201

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Language：English  

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Language：English  

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

DOI： 10.1088/0004-637X/757/2/185

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

DOI： 10.1088/0004-637X/749/1/67

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