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Papers by Munetaka Takeuchi
Proceedings of Japanese Liquid Crystal Society Annual meeting, 1998
The thermal properties of BaFX (X=Cl, Br) crystals by classical molecular dynamics simulation hav... more The thermal properties of BaFX (X=Cl, Br) crystals by classical molecular dynamics simulation have been examined using the Born-Mayer-Huggins potential. The c/a ratio, density, and the linear thermal expansion coefficients along the directions parallel () and perpendicular () to the tetragonal axis have been calculated from the temperature dependence of the lattice parameters (a and c). It was found that both and are of the order of (1.0-2.0) 10-5 K-1 for the bulk BaFBr and (2.5-3.5) 10-5 K-1 for the bulk BaFCl in the temperature range of 300 and 900 K, and show a change of curvature around 500 K. The present method has also been extended to the bulk BaF2 and NaCl for the sake of comparison and confirmation.
Chemischer Informationsdienst, Mar 18, 1986
Journal of Luminescence, May 1, 2000
Some new evidence to determine the origin of the F-aggregate centers located in the near-IR regio... more Some new evidence to determine the origin of the F-aggregate centers located in the near-IR region in BaFX (X"Cl, Br) crystals is demonstrated through a series of measurements and molecular dynamics simulations. Moreover, a new method to determine the concentration of the F centers in the photostimulable materials is also demonstrated. 2000 Elsevier Science B.V. All rights reserved.
Journal of Non-crystalline Solids, Nov 1, 2001
Neutron diraction measurements for H/D isotopically substituted 10, 25 and 33 mol% LiBr hydrated ... more Neutron diraction measurements for H/D isotopically substituted 10, 25 and 33 mol% LiBr hydrated melts and the corresponding MD simulations have been carried out to investigate the intermolecular hydrogen-bonded structure in extremely concentrated aqueous solutions. Observed neutron intermolecular interference terms for the sample solutions with dierent H/D isotope ratios were combined to deduce partial structure factors, a HH Q, a XH Q and a XX Q (X: Li, Br and O), and their Fourier transforms, g HH r, g XH r and g XX r, respectively. Observed g HH r and g XH r for the 10 mol% LiBr solution indicate the well-de®ned ®rst peak located at r 2:4 and 1.9 A, respectively. The latter 1.9 A peak almost disappears for concentrated 25 and 33 mol% LiBr solutions, implying that the hydrogen-bonded network is completely broken. These results agree well with those obtained from the MD simulation. A gradual shift of the ®rst peak position of the simulated g OO r towards a longer-r side is observed with increasing LiBr content, which also re¯ects the collapse of the hydrogen-bonded structure in the solution. The formation of the contact ion pair Li Á Á Á Br À , was con®rmed for highly concentrated 25 and 33 mol% LiBr solutions.
The Journal of Physical Chemistry, 1996
Molecular orbital (MO) calculation and molecular dynamics (MD) simulation were carried out for an... more Molecular orbital (MO) calculation and molecular dynamics (MD) simulation were carried out for an antiferroelectric liquid crystalline molecule, MHPOBC, to understand its conformational property and the origin of bent structure formation in crystalline phase. MO calculations performed for a chiral chain fragment of MHPOBC have determined the conformational state of each bond in the chiral chain. MD simulation, carried out for a system of 64 full MHPOBC molecules, has been able to reproduce the experimentally observed bent conformation and the molecular packing. The present study concludes that (1) the essential conformational feature of the chiral chain of MHPOBC is determined by intramolecular interactions, (2) MHPOBC can adopt two major conformations, i.e., linear and bent conformations, and (3) the bent conformation is selected in the crystalline phase as a consequence of intermolecular steric interactions.
Physica Status Solidi B-basic Solid State Physics, Mar 1, 1999
ABSTRACT
Molecular Simulation, Nov 15, 2004
ABSTRACT
HAL (Le Centre pour la Communication Scientifique Directe), May 31, 2009
poste
Physica Status Solidi B-basic Solid State Physics, Aug 1, 2000
Journal of Crystal Growth, 2001
Abstract In order to determine the distribution of strain inside hemispherical InAs quantum dots ... more Abstract In order to determine the distribution of strain inside hemispherical InAs quantum dots (QDs) embedded in GaAs, molecular dynamics (MD) simulation is applied. Taking into account the distribution of strain, the conduction band minimum (CBM) profile was calculated. We found that the CBM inside the QD is significantly higher than that for the bulk InAs. The electrons tend to be confined in the potential well that exists at the InAs/GaAs interface. As the capping layer thickness of the QD increases, the strain felt by the QD increases but the depth of the potential well decreases, reducing the quantum confinement effect. We believe that MD simulation is a powerful tool that can be used to investigate the distribution of strain in QDs with different compositions, sizes and shapes. Applying the eight-band k·p perturbation Hamiltonian to the simulation results can give a better picture of the real electronic structure of these QDs.
Journal of Crystal Growth, Feb 1, 2000
We have developed a new potential function for classical molecular dynamics (MD) calculations of ... more We have developed a new potential function for classical molecular dynamics (MD) calculations of III–V compound semiconductors. The key idea for the new potential function is incorporation of the ionic nature of the bonds into the conventional Tersoff potential. It has been found that this potential can be used for the simulation of the MBE epitaxial growth for the III–V
Preprints of symposium on liquid crystals, 1994
Preprints of symposium on liquid crystals, 1997
Preprints of symposium on liquid crystals, 1998
Proceedings of Japanese Liquid Crystal Society Annual meeting, 1998
The thermal properties of BaFX (X=Cl, Br) crystals by classical molecular dynamics simulation hav... more The thermal properties of BaFX (X=Cl, Br) crystals by classical molecular dynamics simulation have been examined using the Born-Mayer-Huggins potential. The c/a ratio, density, and the linear thermal expansion coefficients along the directions parallel () and perpendicular () to the tetragonal axis have been calculated from the temperature dependence of the lattice parameters (a and c). It was found that both and are of the order of (1.0-2.0) 10-5 K-1 for the bulk BaFBr and (2.5-3.5) 10-5 K-1 for the bulk BaFCl in the temperature range of 300 and 900 K, and show a change of curvature around 500 K. The present method has also been extended to the bulk BaF2 and NaCl for the sake of comparison and confirmation.
Chemischer Informationsdienst, Mar 18, 1986
Journal of Luminescence, May 1, 2000
Some new evidence to determine the origin of the F-aggregate centers located in the near-IR regio... more Some new evidence to determine the origin of the F-aggregate centers located in the near-IR region in BaFX (X"Cl, Br) crystals is demonstrated through a series of measurements and molecular dynamics simulations. Moreover, a new method to determine the concentration of the F centers in the photostimulable materials is also demonstrated. 2000 Elsevier Science B.V. All rights reserved.
Journal of Non-crystalline Solids, Nov 1, 2001
Neutron diraction measurements for H/D isotopically substituted 10, 25 and 33 mol% LiBr hydrated ... more Neutron diraction measurements for H/D isotopically substituted 10, 25 and 33 mol% LiBr hydrated melts and the corresponding MD simulations have been carried out to investigate the intermolecular hydrogen-bonded structure in extremely concentrated aqueous solutions. Observed neutron intermolecular interference terms for the sample solutions with dierent H/D isotope ratios were combined to deduce partial structure factors, a HH Q, a XH Q and a XX Q (X: Li, Br and O), and their Fourier transforms, g HH r, g XH r and g XX r, respectively. Observed g HH r and g XH r for the 10 mol% LiBr solution indicate the well-de®ned ®rst peak located at r 2:4 and 1.9 A, respectively. The latter 1.9 A peak almost disappears for concentrated 25 and 33 mol% LiBr solutions, implying that the hydrogen-bonded network is completely broken. These results agree well with those obtained from the MD simulation. A gradual shift of the ®rst peak position of the simulated g OO r towards a longer-r side is observed with increasing LiBr content, which also re¯ects the collapse of the hydrogen-bonded structure in the solution. The formation of the contact ion pair Li Á Á Á Br À , was con®rmed for highly concentrated 25 and 33 mol% LiBr solutions.
The Journal of Physical Chemistry, 1996
Molecular orbital (MO) calculation and molecular dynamics (MD) simulation were carried out for an... more Molecular orbital (MO) calculation and molecular dynamics (MD) simulation were carried out for an antiferroelectric liquid crystalline molecule, MHPOBC, to understand its conformational property and the origin of bent structure formation in crystalline phase. MO calculations performed for a chiral chain fragment of MHPOBC have determined the conformational state of each bond in the chiral chain. MD simulation, carried out for a system of 64 full MHPOBC molecules, has been able to reproduce the experimentally observed bent conformation and the molecular packing. The present study concludes that (1) the essential conformational feature of the chiral chain of MHPOBC is determined by intramolecular interactions, (2) MHPOBC can adopt two major conformations, i.e., linear and bent conformations, and (3) the bent conformation is selected in the crystalline phase as a consequence of intermolecular steric interactions.
Physica Status Solidi B-basic Solid State Physics, Mar 1, 1999
ABSTRACT
Molecular Simulation, Nov 15, 2004
ABSTRACT
HAL (Le Centre pour la Communication Scientifique Directe), May 31, 2009
poste
Physica Status Solidi B-basic Solid State Physics, Aug 1, 2000
Journal of Crystal Growth, 2001
Abstract In order to determine the distribution of strain inside hemispherical InAs quantum dots ... more Abstract In order to determine the distribution of strain inside hemispherical InAs quantum dots (QDs) embedded in GaAs, molecular dynamics (MD) simulation is applied. Taking into account the distribution of strain, the conduction band minimum (CBM) profile was calculated. We found that the CBM inside the QD is significantly higher than that for the bulk InAs. The electrons tend to be confined in the potential well that exists at the InAs/GaAs interface. As the capping layer thickness of the QD increases, the strain felt by the QD increases but the depth of the potential well decreases, reducing the quantum confinement effect. We believe that MD simulation is a powerful tool that can be used to investigate the distribution of strain in QDs with different compositions, sizes and shapes. Applying the eight-band k·p perturbation Hamiltonian to the simulation results can give a better picture of the real electronic structure of these QDs.
Journal of Crystal Growth, Feb 1, 2000
We have developed a new potential function for classical molecular dynamics (MD) calculations of ... more We have developed a new potential function for classical molecular dynamics (MD) calculations of III–V compound semiconductors. The key idea for the new potential function is incorporation of the ionic nature of the bonds into the conventional Tersoff potential. It has been found that this potential can be used for the simulation of the MBE epitaxial growth for the III–V
Preprints of symposium on liquid crystals, 1994
Preprints of symposium on liquid crystals, 1997
Preprints of symposium on liquid crystals, 1998