The Experts below are selected from a list of 102 Experts worldwide ranked by ideXlab platform

Haruyuki Inui - One of the best experts on this subject based on the ideXlab platform.

  • Structural
    2015
    Co-Authors: Haruyuki Inui, Akihiro Fujii, Katsushi Tanaka, Hiroki Sakamoto, Acta Crystallographica Section B, Akihiro A Fujii, Katsushi Tanaka B Hiroki, Kazuo Ishizukac
    Abstract:

    New Electron Diffraction Method to identify the chirality of enantiomorphic crystal

  • Enantiomorph identification of crystals belonging to the point groups of 622 and 6 by convergent-beam Electron Diffraction Method
    Intermetallics, 2007
    Co-Authors: Akihiro Fujii, Katsushi Tanaka, Hiroki Sakamoto, Satoshi Fujio, Haruyuki Inui
    Abstract:

    Abstract A CBED Method proposed by the present authors for chiral identification of enantiomorphic crystals has been successfully applied to crystals with the point groups of 622 and 6. The intensity asymmetry of ZOLZ and/or FOLZ reflections of the Bijvoet pairs is utilized for enantiomorph identification and such intensity asymmetry is noted regardless of beam convergence angle but the extent to which the asymmetry is noted depends on crystal thickness and accelerating voltage. The crystal thickness should be smaller than the extinction distance of relevant reflections that constitute ‘umweganregung’ in multiple scattering, which is responsible for the intensity asymmetry. As a result, the maximum crystal thickness, below which the asymmetric intensity distribution of Bijvoet reflections is evident, increases as the accelerating voltage is increased. When the crystal thickness is small, however, the intensity asymmetry is more pronounced as the accelerating voltage is decreased due to the increased propensity of multiple scattering.

  • enantiomorph identification of transition metal disilicides with the c40 structure the space group of p6222 and p6422 by new convergent beam Electron Diffraction Method
    Acta Materialia, 2005
    Co-Authors: Hiroki Sakamoto, Katsushi Tanaka, Akihiro Fujii, Haruyuki Inui
    Abstract:

    Abstract The new CBED Method we proposed recently for enantiomorph identification has been applied to transition-metal disilicides with the C40 structure (the space groups of P6222 and P6422). The enantiomorph can be easily identified by simply inspecting the intensity asymmetry of Bijvoet pairs of ZOLZ and/or FOLZ reflections in a CBED pattern taken along an appropriate zone-axis orientation. The way for enantiomorph identification with the present Method is altered neither with the changes in the lattice parameters and averaged atomic scattering factors in the range expected for real C40 disilicide crystals of multi-component nor with the atom position parameter for Si atoms in 6j sites. The Method is successfully applied to real C40 disilicides, and our single crystals of VSi2, CrSi2, TaSi2 and Mo(Si0.85Al0.15)2 are determined to belong to P6422 whereas that of NbSi2 is determined to belong to P6222. These results are all consistent with those of our previous X-ray Diffraction study.

  • New Electron Diffraction Method to identify the chirality of enantiomorphic crystals
    Acta Crystallographica Section B Structural Science, 2003
    Co-Authors: Haruyuki Inui, Akihiro Fujii, Katsushi Tanaka, Hiroki Sakamoto, Kazuo Ishizuka
    Abstract:

    A new CBED (convergent-beam Electron Diffraction) Method is proposed for the identification of the chirality of enantiomorphic crystals, in which asymmetry in the intensity of the reflections of Bijvoet pairs in an experimental symmetrical zone-axis CBED pattern is compared with that of a computer-simulated CBED pattern. The intensity difference for reflections of these Bijvoet pairs results from multiple scattering (dynamical nature of Electron Diffraction) among relevant Bijvoet pairs of reflections, each pair of which has identical amplitude and different phase angles. Therefore, the crystal thickness where chiral identification is made with the present Method is limited by the extinction distance of Bijvoet pairs of reflections relevant to multiple scattering to produce the intensity asymmetry, which is usually of the order of a few tens of nanometers. With the present Method, a single CBED pattern is sufficient and chiral identification can be made for all the possible enantiomorphic crystals that are allowed to exist in crystallography.

Hiroki Sakamoto - One of the best experts on this subject based on the ideXlab platform.

  • Structural
    2015
    Co-Authors: Haruyuki Inui, Akihiro Fujii, Katsushi Tanaka, Hiroki Sakamoto, Acta Crystallographica Section B, Akihiro A Fujii, Katsushi Tanaka B Hiroki, Kazuo Ishizukac
    Abstract:

    New Electron Diffraction Method to identify the chirality of enantiomorphic crystal

  • Enantiomorph identification of crystals belonging to the point groups of 622 and 6 by convergent-beam Electron Diffraction Method
    Intermetallics, 2007
    Co-Authors: Akihiro Fujii, Katsushi Tanaka, Hiroki Sakamoto, Satoshi Fujio, Haruyuki Inui
    Abstract:

    Abstract A CBED Method proposed by the present authors for chiral identification of enantiomorphic crystals has been successfully applied to crystals with the point groups of 622 and 6. The intensity asymmetry of ZOLZ and/or FOLZ reflections of the Bijvoet pairs is utilized for enantiomorph identification and such intensity asymmetry is noted regardless of beam convergence angle but the extent to which the asymmetry is noted depends on crystal thickness and accelerating voltage. The crystal thickness should be smaller than the extinction distance of relevant reflections that constitute ‘umweganregung’ in multiple scattering, which is responsible for the intensity asymmetry. As a result, the maximum crystal thickness, below which the asymmetric intensity distribution of Bijvoet reflections is evident, increases as the accelerating voltage is increased. When the crystal thickness is small, however, the intensity asymmetry is more pronounced as the accelerating voltage is decreased due to the increased propensity of multiple scattering.

  • enantiomorph identification of transition metal disilicides with the c40 structure the space group of p6222 and p6422 by new convergent beam Electron Diffraction Method
    Acta Materialia, 2005
    Co-Authors: Hiroki Sakamoto, Katsushi Tanaka, Akihiro Fujii, Haruyuki Inui
    Abstract:

    Abstract The new CBED Method we proposed recently for enantiomorph identification has been applied to transition-metal disilicides with the C40 structure (the space groups of P6222 and P6422). The enantiomorph can be easily identified by simply inspecting the intensity asymmetry of Bijvoet pairs of ZOLZ and/or FOLZ reflections in a CBED pattern taken along an appropriate zone-axis orientation. The way for enantiomorph identification with the present Method is altered neither with the changes in the lattice parameters and averaged atomic scattering factors in the range expected for real C40 disilicide crystals of multi-component nor with the atom position parameter for Si atoms in 6j sites. The Method is successfully applied to real C40 disilicides, and our single crystals of VSi2, CrSi2, TaSi2 and Mo(Si0.85Al0.15)2 are determined to belong to P6422 whereas that of NbSi2 is determined to belong to P6222. These results are all consistent with those of our previous X-ray Diffraction study.

  • New Electron Diffraction Method to identify the chirality of enantiomorphic crystals
    Acta Crystallographica Section B Structural Science, 2003
    Co-Authors: Haruyuki Inui, Akihiro Fujii, Katsushi Tanaka, Hiroki Sakamoto, Kazuo Ishizuka
    Abstract:

    A new CBED (convergent-beam Electron Diffraction) Method is proposed for the identification of the chirality of enantiomorphic crystals, in which asymmetry in the intensity of the reflections of Bijvoet pairs in an experimental symmetrical zone-axis CBED pattern is compared with that of a computer-simulated CBED pattern. The intensity difference for reflections of these Bijvoet pairs results from multiple scattering (dynamical nature of Electron Diffraction) among relevant Bijvoet pairs of reflections, each pair of which has identical amplitude and different phase angles. Therefore, the crystal thickness where chiral identification is made with the present Method is limited by the extinction distance of Bijvoet pairs of reflections relevant to multiple scattering to produce the intensity asymmetry, which is usually of the order of a few tens of nanometers. With the present Method, a single CBED pattern is sufficient and chiral identification can be made for all the possible enantiomorphic crystals that are allowed to exist in crystallography.

Akihiro Fujii - One of the best experts on this subject based on the ideXlab platform.

  • Structural
    2015
    Co-Authors: Haruyuki Inui, Akihiro Fujii, Katsushi Tanaka, Hiroki Sakamoto, Acta Crystallographica Section B, Akihiro A Fujii, Katsushi Tanaka B Hiroki, Kazuo Ishizukac
    Abstract:

    New Electron Diffraction Method to identify the chirality of enantiomorphic crystal

  • Enantiomorph identification of crystals belonging to the point groups of 622 and 6 by convergent-beam Electron Diffraction Method
    Intermetallics, 2007
    Co-Authors: Akihiro Fujii, Katsushi Tanaka, Hiroki Sakamoto, Satoshi Fujio, Haruyuki Inui
    Abstract:

    Abstract A CBED Method proposed by the present authors for chiral identification of enantiomorphic crystals has been successfully applied to crystals with the point groups of 622 and 6. The intensity asymmetry of ZOLZ and/or FOLZ reflections of the Bijvoet pairs is utilized for enantiomorph identification and such intensity asymmetry is noted regardless of beam convergence angle but the extent to which the asymmetry is noted depends on crystal thickness and accelerating voltage. The crystal thickness should be smaller than the extinction distance of relevant reflections that constitute ‘umweganregung’ in multiple scattering, which is responsible for the intensity asymmetry. As a result, the maximum crystal thickness, below which the asymmetric intensity distribution of Bijvoet reflections is evident, increases as the accelerating voltage is increased. When the crystal thickness is small, however, the intensity asymmetry is more pronounced as the accelerating voltage is decreased due to the increased propensity of multiple scattering.

  • enantiomorph identification of transition metal disilicides with the c40 structure the space group of p6222 and p6422 by new convergent beam Electron Diffraction Method
    Acta Materialia, 2005
    Co-Authors: Hiroki Sakamoto, Katsushi Tanaka, Akihiro Fujii, Haruyuki Inui
    Abstract:

    Abstract The new CBED Method we proposed recently for enantiomorph identification has been applied to transition-metal disilicides with the C40 structure (the space groups of P6222 and P6422). The enantiomorph can be easily identified by simply inspecting the intensity asymmetry of Bijvoet pairs of ZOLZ and/or FOLZ reflections in a CBED pattern taken along an appropriate zone-axis orientation. The way for enantiomorph identification with the present Method is altered neither with the changes in the lattice parameters and averaged atomic scattering factors in the range expected for real C40 disilicide crystals of multi-component nor with the atom position parameter for Si atoms in 6j sites. The Method is successfully applied to real C40 disilicides, and our single crystals of VSi2, CrSi2, TaSi2 and Mo(Si0.85Al0.15)2 are determined to belong to P6422 whereas that of NbSi2 is determined to belong to P6222. These results are all consistent with those of our previous X-ray Diffraction study.

  • New Electron Diffraction Method to identify the chirality of enantiomorphic crystals
    Acta Crystallographica Section B Structural Science, 2003
    Co-Authors: Haruyuki Inui, Akihiro Fujii, Katsushi Tanaka, Hiroki Sakamoto, Kazuo Ishizuka
    Abstract:

    A new CBED (convergent-beam Electron Diffraction) Method is proposed for the identification of the chirality of enantiomorphic crystals, in which asymmetry in the intensity of the reflections of Bijvoet pairs in an experimental symmetrical zone-axis CBED pattern is compared with that of a computer-simulated CBED pattern. The intensity difference for reflections of these Bijvoet pairs results from multiple scattering (dynamical nature of Electron Diffraction) among relevant Bijvoet pairs of reflections, each pair of which has identical amplitude and different phase angles. Therefore, the crystal thickness where chiral identification is made with the present Method is limited by the extinction distance of Bijvoet pairs of reflections relevant to multiple scattering to produce the intensity asymmetry, which is usually of the order of a few tens of nanometers. With the present Method, a single CBED pattern is sufficient and chiral identification can be made for all the possible enantiomorphic crystals that are allowed to exist in crystallography.

Katsushi Tanaka - One of the best experts on this subject based on the ideXlab platform.

  • Structural
    2015
    Co-Authors: Haruyuki Inui, Akihiro Fujii, Katsushi Tanaka, Hiroki Sakamoto, Acta Crystallographica Section B, Akihiro A Fujii, Katsushi Tanaka B Hiroki, Kazuo Ishizukac
    Abstract:

    New Electron Diffraction Method to identify the chirality of enantiomorphic crystal

  • Enantiomorph identification of crystals belonging to the point groups of 622 and 6 by convergent-beam Electron Diffraction Method
    Intermetallics, 2007
    Co-Authors: Akihiro Fujii, Katsushi Tanaka, Hiroki Sakamoto, Satoshi Fujio, Haruyuki Inui
    Abstract:

    Abstract A CBED Method proposed by the present authors for chiral identification of enantiomorphic crystals has been successfully applied to crystals with the point groups of 622 and 6. The intensity asymmetry of ZOLZ and/or FOLZ reflections of the Bijvoet pairs is utilized for enantiomorph identification and such intensity asymmetry is noted regardless of beam convergence angle but the extent to which the asymmetry is noted depends on crystal thickness and accelerating voltage. The crystal thickness should be smaller than the extinction distance of relevant reflections that constitute ‘umweganregung’ in multiple scattering, which is responsible for the intensity asymmetry. As a result, the maximum crystal thickness, below which the asymmetric intensity distribution of Bijvoet reflections is evident, increases as the accelerating voltage is increased. When the crystal thickness is small, however, the intensity asymmetry is more pronounced as the accelerating voltage is decreased due to the increased propensity of multiple scattering.

  • enantiomorph identification of transition metal disilicides with the c40 structure the space group of p6222 and p6422 by new convergent beam Electron Diffraction Method
    Acta Materialia, 2005
    Co-Authors: Hiroki Sakamoto, Katsushi Tanaka, Akihiro Fujii, Haruyuki Inui
    Abstract:

    Abstract The new CBED Method we proposed recently for enantiomorph identification has been applied to transition-metal disilicides with the C40 structure (the space groups of P6222 and P6422). The enantiomorph can be easily identified by simply inspecting the intensity asymmetry of Bijvoet pairs of ZOLZ and/or FOLZ reflections in a CBED pattern taken along an appropriate zone-axis orientation. The way for enantiomorph identification with the present Method is altered neither with the changes in the lattice parameters and averaged atomic scattering factors in the range expected for real C40 disilicide crystals of multi-component nor with the atom position parameter for Si atoms in 6j sites. The Method is successfully applied to real C40 disilicides, and our single crystals of VSi2, CrSi2, TaSi2 and Mo(Si0.85Al0.15)2 are determined to belong to P6422 whereas that of NbSi2 is determined to belong to P6222. These results are all consistent with those of our previous X-ray Diffraction study.

  • New Electron Diffraction Method to identify the chirality of enantiomorphic crystals
    Acta Crystallographica Section B Structural Science, 2003
    Co-Authors: Haruyuki Inui, Akihiro Fujii, Katsushi Tanaka, Hiroki Sakamoto, Kazuo Ishizuka
    Abstract:

    A new CBED (convergent-beam Electron Diffraction) Method is proposed for the identification of the chirality of enantiomorphic crystals, in which asymmetry in the intensity of the reflections of Bijvoet pairs in an experimental symmetrical zone-axis CBED pattern is compared with that of a computer-simulated CBED pattern. The intensity difference for reflections of these Bijvoet pairs results from multiple scattering (dynamical nature of Electron Diffraction) among relevant Bijvoet pairs of reflections, each pair of which has identical amplitude and different phase angles. Therefore, the crystal thickness where chiral identification is made with the present Method is limited by the extinction distance of Bijvoet pairs of reflections relevant to multiple scattering to produce the intensity asymmetry, which is usually of the order of a few tens of nanometers. With the present Method, a single CBED pattern is sufficient and chiral identification can be made for all the possible enantiomorphic crystals that are allowed to exist in crystallography.

Anatolii N. Rykov - One of the best experts on this subject based on the ideXlab platform.

  • Molecular structure study of 1,2,3-trimethyldiaziridine by means of gas Electron Diffraction Method
    Structural Chemistry, 2019
    Co-Authors: Ilya I. Marochkin, Vladimir V. Kuznetsov, Anatolii N. Rykov, Nina N. Makhova, Igor F. Shishkov
    Abstract:

    The molecular structure of 1,2,3-trimethyldiaziridine has been determined from the gas-phase Electron Diffraction data supplemented spectral and quantum chemical calculations. The configuration of studied compound incorporates trans- position of methyl groups attached to nitrogen atoms of diaziridine cycle. The following principal structural parameters were determined ( r _h1 bond lengths in Å, bond angles in degrees with 3σ in parentheses): r (N–C), 1.489(9); r (N–N), 1.480(15); r (C–C), 1.503(15); ∠NCN, 61.5(9); ∠(H_3C)CN, 124.0(15). The obtained structural parameters of 1,2,3-trimethyldiaziridine were compared with those for structural analogues. The gaseous standard enthalpy of formation of 1,2,3-trimethyldiaziridine was estimated to be 176.2 ± 5.0 kJ/mol.

  • 3 cyclopropyl 1 2 dimethyldiaziridine synthesis and study of molecular structure by gas Electron Diffraction Method
    Structural Chemistry, 2018
    Co-Authors: Ekaterina P Altova, Ilya I. Marochkin, Anatolii N. Rykov, Nina N. Makhova, V Kuznetsov, Igor F. Shishkov
    Abstract:

    The molecular structure and conformational behavior of 3-cyclopropyl-1,2-dimethyldiaziridine have been for the first time experimentally studied by gas-phase Electron Diffraction and quantum chemical calculations. The two most stable conformers at 298 K possess anti and gauche mutual ring orientation (with prevalence of the anti conformer) whereas only one anti conformer is observed in solution. The determined structural parameters of gaseous 3-cyclopropyl-1,2-dimethyldiaziridine have been compared with those for 3,3-bidiaziridine structural analogues in the crystal phase. The simple and convenient procedure for the synthesis of 3-cyclopropyl-1,2-dimethyldiaziridine comprising cyclopropane and diaziridine rings in one molecule was developed. The standard enthalpy of formation of 3-cyclopropyl-1,2-dimethyldiaziridine in the gas phase was calculated using Gaussian-4 theory, yielding value of 281.9 ± 5.0 kJ/mol.

  • molecular structure of tryptamine in gas phase according to gas Electron Diffraction Method and quantum chemistry calculations
    Journal of Molecular Structure, 2017
    Co-Authors: Ilya I. Marochkin, Anatolii N. Rykov, Ekaterina P Altova, Igor F. Shishkov
    Abstract:

    Abstract The molecular structure of tryptamine was studied by gas-phase Electron Diffraction (GED) and quantum chemical calculations (DFT/B3LYP and MP2 Methods with cc-pVTZ basis set). The best fit of the experimental scattering intensities (R-factor = 3.8%) was obtained for the four-conformer model. The experimental structural parameters are found to be in good agreement with the results of theoretical calculations. The geometric parameters of gaseous tryptamine are compared with those in the crystal phase. The standard enthalpy of formation of tryptamine in the gas phase was calculated using Gaussian-4 theory, yielding value of 133.6 ± 3.3 kJ/mol.

  • conformational and bonding properties of 3 3 dimethyl and 6 6 dimethyl 1 5 diazabicyclo 3 1 0 hexane a case study employing the monte carlo Method in gas Electron Diffraction
    Journal of Physical Chemistry A, 2015
    Co-Authors: Yury V Vishnevskiy, Anatolii N. Rykov, Jan Schwabedissen, V V Kuznetsov, Nina N. Makhova
    Abstract:

    Gas-phase structures of two isomers of dimethyl-substituted 1,5-diazabicyclo[3.1.0]hexanes, namely, 3,3-dimethyl- and 6,6-dimethyl-1,5-diazabicyclo[3.1.0]hexane molecules, have been determined by gas Electron Diffraction Method. A new approach based on the Monte Carlo Method has been developed and used for the analysis of precision and accuracy of the refined structures. It was found that at 57 °C 3,3-dimethyl derivative exists as a mixture of chair and boat conformers with abundances 68(8)% and 32(8)%, respectively. 6,6-Dimethyl-1,5-diazabicyclo[3.1.0]hexane at 50 °C has only one stable conformation with planar 5-ring within error limits. Theoretical calculations predict that the 6,6-dimethyl isomer is more stable in comparison to the 3,3-dimethyl isomer with energy difference 3-5 kcal mol(-1). In order to explain the relative stability and bonding properties of different structures the natural bond orbitals (NBO), atoms in molecules (AIM), and interacting quantum atoms (IQA) analyses were performed.

  • interplay of experiment and theory determination of an accurate equilibrium structure of 1 methyluracil by the gas Electron Diffraction Method and coupled cluster computations
    Journal of Physical Chemistry A, 2013
    Co-Authors: Natalja Vogt, Ilya I. Marochkin, Anatolii N. Rykov, O V Dorofeeva
    Abstract:

    As far as fundamental knowledge is concerned, the methyl derivatives of uracil can be considered as the simplest objects for studying the structural effects due to the substitution in the pyrimidyne nucleobases. From this point of view, 1-methyluracil is of special importance in biochemistry because uracil attaches ribose in ribonucleic acid (RNA) just precisely at the N1 atom. The semi-experimental equilibrium structure (rese) of 1-methyluracil has been determined for the first time by the gas Electron Diffraction (GED) Method taking into account rovibrational corrections to the thermal-average internuclear distances calculated with harmonic and anharmonic (cubic) MP2/cc-pVTZ force constants with consideration of the methyl torsion as a large-amplitude motion. For the first time, the structure of the molecule has been optimized by the very time-consuming coupled-cluster Method with single and double excitations and perturbative treatment of connected triples using the correlation-consistent polarized wei...