JaLCDOI 10.18926/15402
フルテキストURL Mem_Fac_Eng_OU_30_2_27.pdf
著者 東辻 浩夫| 岸本 篤也| 東辻 千枝子|
抄録 The behavior of the Yukawa system in external one-dimensional force fields is analyzed by the molecular dynamics simulation. The formation of layered structures at low temperatures is observed and the relation between the number of layers and characteristic parameters of the system is obtained. Since the Yukawa system serves as a model of clouds of dust particles in plasmas (dusty plasma) which play an important role in plasma processes of semiconductor engineering, the results may be useful to control the quality of semiconductor wafers in such processes. In simulations, periodic boundary conditions are imposed in two dimensions and deformations of periodic boundaries are allowed in order to reduce the effect of boundaries without giving too much constraint on the symmetry.
出版物タイトル Memoirs of the Faculty of Engineering, Okayama University
発行日 1996-03-29
30巻
2号
開始ページ 27
終了ページ 37
ISSN 0475-0071
言語 English
論文のバージョン publisher
NAID 120002307582
JaLCDOI 10.18926/14058
フルテキストURL Mem_Fac_Eng_OU_42_44.pdf
著者 Ogawa Takafumi| 鶴田 健二| 東辻 千枝子| 東辻 浩夫| Hiroshi Iyetomi|
抄録 To analyze vibrational properties of Si crystal with a single charge-neutral vacancy, we perform large-scale simulations based on tight-binding molecular-dynamics method. Vibrational modes and frequencies are obtained by diagonalizing dynamical matrix within a harmonic approximation. Results indicate that there exist vibrational modes spatially localized around the vacancy and large frequency shifts associated with the localized modes contribute significantly to reduction of the vibrational free energy.
出版物タイトル Memoirs of the Faculty of Engineering, Okayama University
発行日 2008-01
42巻
1号
開始ページ 44
終了ページ 47
ISSN 0475-0071
言語 English
論文のバージョン publisher
NAID 120002308412
JaLCDOI 10.18926/15424
フルテキストURL Mem_Fac_Eng_OU_29_2_67.pdf
著者 東辻 千枝子| Matsubara Takeo| Obuchi Masumi|
抄録 The π-electron band of C(60) molecule has been obtained by the tight binding approximation. Application of molecular orbital wave functions derived on the basis of the optimized bond orbital model gives, with simpler calculations, the results in satisfactory agreement with those of previous theoretical analyses.
出版物タイトル Memoirs of the Faculty of Engineering, Okayama University
発行日 1995-03-27
29巻
2号
開始ページ 67
終了ページ 76
ISSN 0475-0071
言語 English
論文のバージョン publisher
NAID 120002307408
JaLCDOI 10.18926/19636
フルテキストURL Mem_Fac_Eng_OU_32_23.pdf
著者 東辻 浩夫| 岸本 篤也| 東辻 千枝子|
抄録 Parameters characterizing the structure ot confined Yukawa system are estimated for 'dusty plasmas', clouds of charged macroscopic particles formed near the boundary between plasma and the sheath and leviated by negatively biased electrode. When we have dust particles with different ratios of charge to mass, they form a two-dimensional Yukawa mixture or separate two-dimensional one-companent Yukawa systems, depending on the charge density in the sheath and number density of dust particles. In order to provide a basis for numerical simulations on Yukawa mixtures including Coulombic case, we summarize mathematical expressions necessary for molecular dynamics.
出版物タイトル Memoirs of the Faculty of Engineering, Okayama University
発行日 1998-04-20
32巻
1-2号
開始ページ 23
終了ページ 41
ISSN 0475-0071
言語 English
論文のバージョン publisher
NAID 120002309150
JaLCDOI 10.18926/15166
フルテキストURL Mem_Fac_Eng_OU_31_1_19.pdf
著者 東辻 浩夫| 岸本 篤也| 東辻 千枝子|
抄録 As a model of dusty plasmas in external fields, Yuka.wa system in a one-dimensional external field is analyzed by molecular dynamics simulations and theoretical approaches. It is shown that particles form clear thin layers (sheets) at low temperatures and the number of layers changes discretely with characteristic parameters of the system, accompanying the rearrangements of whole system from nearly equipartitioned layers to also nearly equipartitioned layers. The number, positions and populations of layers are obtained as functions of characteristic parameters. The shell (sheet) model which has been successful for confined one-component plasmas is extended to this system and results of numerical experiments are reproduced to a good accuracy. The effect of cohesive energy in each layer is of essential importance to reproduce discrete changes in the number of sheets.
出版物タイトル Memoirs of the Faculty of Engineering, Okayama University
発行日 1996-12-27
31巻
1号
開始ページ 19
終了ページ 33
ISSN 0475-0071
言語 English
論文のバージョン publisher
NAID 120002307616
JaLCDOI 10.18926/14120
フルテキストURL Mem_Fac_Eng_OU_40_1_36.pdf
著者 内田 厚| 東辻 千枝子| 鶴田 健二| 東辻 浩夫|
抄録 We present a Stochastic-Difference-Equation (SDE) approach to long time-scale molecular dynamics (MD) simulations, which are required for nanosecond-scale phenomena. In this method, the MD trajectory in a fixed time period is obtained as a stationary solution of an action functional based on an error accumulation of the equation of motion along the path, thus reducing the problem to a boundary-value problem, instead of an initial-value problem in the ordinary MD method. We apply the method to formation processes of Cu thin film via nanocluster deposition onto a substrate. The applicability of the SDE algorithm to the problem and the effects of the choice of SDE parameters on the optimization processes of configuration pathway are examined.
出版物タイトル Memoirs of the Faculty of Engineering, Okayama University
発行日 2006-01
40巻
1号
開始ページ 36
終了ページ 39
ISSN 0475-0071
言語 English
論文のバージョン publisher
NAID 120002308517
JaLCDOI 10.18926/14061
フルテキストURL Mem_Fac_Eng_OU_42_56.pdf
著者 Miyake Takashi| 東辻 千枝子| Nakanishi Kenta| 鶴田 健二| 東辻 浩夫|
抄録 We analyze the ground state of the two-dimensional quantum system of electrons confined in a parabolic potential with the system size around 100. We map the system onto a classical system on the basis of the classical-map hypernetted-chain (CHNC) method which has been proven to work in the integral-equation-based analyses of uniform unbounded systems and then apply classical numerical simulations. We find that the confined system undergoes the transition to the spin polarized state with the decrease of the average density and the corresponding critical value is as low as rs ∼ 0.3 in terms of the usual rs parameter estimated for the average density. As the ground state for given value of the rs parameter, our data give the critical value for the transition around 20 which is consistent with the known possibility. The advantage of our method is a direct applicability to geometrically complex systems which are difficult to analyze by integral equations. The application to the structure like quantum dots reported here is the first example of such applications.
出版物タイトル Memoirs of the Faculty of Engineering, Okayama University
発行日 2008-01
42巻
1号
開始ページ 56
終了ページ 59
ISSN 0475-0071
言語 English
論文のバージョン publisher
NAID 120002308633
JaLCDOI 10.18926/19674
フルテキストURL Mem_Fac_Eng_OU_33_2_71.pdf
著者 鶴田 健二| 東辻 浩夫| 東辻 千枝子|
抄録 A parallel tight-binding molecular dynamics with an order-N [O(N))] algorithm is implemented to perform large-scale simulation of nanostructured materials. The algorithm is based on the Fermi-operator expansion of an electronic energy and force, and we present its basic formalisms. Accuracy necessary for molecular-dynamics simulations can be obtained by a proper truncation in the expansion. Parallel efficiency on a parallel PC cluster shows nearly ideal scaling behavior with respect to the number of processors. Applicability of the method to a silicon-carbide system is examined.
出版物タイトル Memoirs of the Faculty of Engineering, Okayama University
発行日 1999-04-27
33巻
2号
開始ページ 71
終了ページ 77
ISSN 0475-0071
言語 English
論文のバージョン publisher
NAID 120002309027
JaLCDOI 10.18926/14059
フルテキストURL Mem_Fac_Eng_OU_42_48.pdf
著者 東辻 千枝子| Miyake Takashi| Nakanishi Kenta| 鶴田 健二| 東辻 浩夫|
抄録 Based on the mapping introduced by the classical-map hypernetted-chain (CHNC) method, classical numerical simulations, Monte Carlo and molecular dynamics, have been applied to the twodimensional electron fluid and the results are compared with those of quantum Monte Carlo simulations hitherto reported. It is shown that polarization properties of the ground state obtained by the diffusion Monte Carlo method are reproduced within the accuracy of quantum simulations by both of two mapping functions for the quantum temperature which have been proposed within the CHNC method. These results may serve as the basis of numerical simulations based on the CHNC method which are applicable to finite non-periodic systems like quantum dots and systems at finite temperatures.
出版物タイトル Memoirs of the Faculty of Engineering, Okayama University
発行日 2008-01
42巻
1号
開始ページ 48
終了ページ 52
ISSN 0475-0071
言語 English
論文のバージョン publisher
NAID 120002308425
JaLCDOI 10.18926/19637
フルテキストURL Mem_Fac_Eng_OU_32_43.pdf
著者 東辻 千枝子| Matsubara Takeo|
抄録 Large isotope effects have been observed in various kinds of hydrogen bonded ferro / antiferroelectrics. In clariflying their origin, themodynamic properties of the hydrogen bond are of essential importance. Two numerical methods are applied to analyze the model for isolated hydrogen bond at finite temperatures and the results of excited energy levels of proton or deuteron are examined. It is found that the second excited state is not far enough from the first excited state to be neglected discussing themodynamic properties of hydrogen especially in their ordered states.
出版物タイトル Memoirs of the Faculty of Engineering, Okayama University
発行日 1998-04-20
32巻
1-2号
開始ページ 43
終了ページ 54
ISSN 0475-0071
言語 English
論文のバージョン publisher
NAID 120002309098
JaLCDOI 10.18926/15461
フルテキストURL Mem_Fac_Eng_OU_28_2_53.pdf
著者 東辻 千枝子| Matsubara Takeo| Miyata Satoru|
抄録 One of the best known solid solution of perovskites is the PbTiO(3)-PbZrO(3) system which is usually abbreviated as PZT. In the phase diagram of this system, there is a drastic phase change from tetragonal to rhombohedral at the molar ratio around 50:50. The PZT crystals are widely used as a practical piezoelectric material because of its very strong piezoelectric effect near this morphotropic phase boundary. We try to explain this anomaly in piezoelectric constant by a phenomenological theory.
出版物タイトル Memoirs of the Faculty of Engineering, Okayama University
発行日 1994-03-15
28巻
2号
開始ページ 53
終了ページ 58
ISSN 0475-0071
言語 English
論文のバージョン publisher
NAID 120002307223
JaLCDOI 10.18926/20012
フルテキストURL Mem_Fac_Eng_OU_29_1_15.pdf
著者 東辻 千枝子| Matsubara, Takeo| Obuchi, Masumi|
抄録 A molecular orbital approach to the electronic structure of C(60) molecule is formulated on the basis of optimized bond orbital model and the stability of the truncated icosahedron structure is examined.
出版物タイトル Memoirs of the Faculty of Engineering, Okayama University
発行日 1994-11-30
29巻
1号
開始ページ 15
終了ページ 22
ISSN 0475-0071
言語 English
論文のバージョン publisher
NAID 120002310919
JaLCDOI 10.18926/15358
フルテキストURL Mem_Fac_Eng_OU_35_63.pdf
著者 Shinomiya Shigeru| 東辻 千枝子| 鶴田 健二| 東辻 浩夫|
抄録 We present a theoretical study of Si(1-x)Ge(x) alloys based on tight-binding molecular dynamics (TBMD) calculations. First, we introduce a new set of nonorthogonal tight-binding parameters for silicon and germanium based on the previous work by Menon and Subbaswamy [Phys. Rev. B 55, 9231 (1997); J. Phys: Condens. Matter 10, 10991 (1998)]. We then apply the method to structural analyses of Si(1-x)Ge(x) alloys. The equilibrium volume and atomic structure for a given x are obtained by the TBMD method. We also calculate the bulk modulus B, elastic constants C(11), C(12) and C(44) as a function of x. The results show that the moduli vary monotonically, but nonlinearly, between the values of Si crystal and Ge crystal. The validity of the results is also discussed.
出版物タイトル Memoirs of the Faculty of Engineering, Okayama University
発行日 2001-03-27
35巻
1-2号
開始ページ 63
終了ページ 75
ISSN 0475-0071
言語 English
論文のバージョン publisher
NAID 120002307673
JaLCDOI 10.18926/19673
フルテキストURL Mem_Fac_Eng_OU_33_2_61.pdf
著者 東辻 浩夫| 鶴田 健二| 東辻 千枝子|
抄録 The behavior of multicomponent plasmas in the Penning-Malmberg traps is discussed with the parameters corresponding to experiments with antiprotons and cryogenic electrons. The relaxation times for the energy transfer antiprotons to electrons and between parallel and perpendicular components of electrons are estimated. It is shown that, depending on the values of parameters, both the former and the latter can be the bottleneck in the cooling process.
出版物タイトル Memoirs of the Faculty of Engineering, Okayama University
発行日 1999-04-27
33巻
2号
開始ページ 61
終了ページ 69
ISSN 0475-0071
言語 English
論文のバージョン publisher
NAID 120002309106
JaLCDOI 10.18926/15381
フルテキストURL Mem_Fac_Eng_OU_30_1_75.pdf
著者 東辻 浩夫| 井上 嘉彦| 岸本 篤也| 東辻 千枝子| 奈良 重俊|
抄録 Molecular dynamics of the Yukawa system, the system of particles interacting via the Yukawa or the screened Coulomb potential, are formulated for various statistical ensembles and external conditions. The Yukawa potential smoothly interpolates the long-range Coulomb and the short-range interactions by adjusting a single parameter, the screening length. In order to reduce the effect of boundaries, the periodic boundary conditions are imposed and the deformations of the fundamental vectors of periodicity are taken into account. Ewald-type expressions for interaction energy, force, and kinematic pressure are given explicitly.
出版物タイトル Memoirs of the Faculty of Engineering, Okayama University
発行日 1995-12-28
30巻
1号
開始ページ 75
終了ページ 87
ISSN 0475-0071
言語 English
論文のバージョン publisher
NAID 120002307479
JaLCDOI 10.18926/15361
フルテキストURL Mem_Fac_Eng_OU_35_77.pdf
著者 Kishimoto Tokunari| 東辻 千枝子| 鶴田 健二| 東辻 浩夫|
抄録 In order to perform the large-scale molecular dynamics simulation of the Yukawa system, a mathematical expression for molecular dynamics using the fast multipole method is described. The model simulations are also performed to test the performance of our implementation of the FMM.
出版物タイトル Memoirs of the Faculty of Engineering, Okayama University
発行日 2001-03-27
35巻
1-2号
開始ページ 77
終了ページ 95
ISSN 0475-0071
言語 English
論文のバージョン publisher
NAID 120002307940
JaLCDOI 10.18926/14119
フルテキストURL Mem_Fac_Eng_OU_40_1_31.pdf
著者 小川 貴史| 東辻 千枝子| 鶴田 健二| 東辻 浩夫|
抄録 We analyze the melting of spherical Yukawa clusters by Monte Carlo simulations. Spherical clusters are expected to be found in dusty plasmas in an isotropic environment such as microgravity and serve as a model for classical clusters. We obtain the specific heat through fluctuations of the potential energy and identify its peak as the transition temperature. Melting temperatures are compared with those of bulk Yukawa systems and it is confirmed that the melting temperature increases and approaches the bulk value with the increase of the system size.
出版物タイトル Memoirs of the Faculty of Engineering, Okayama University
発行日 2006-01
40巻
1号
開始ページ 31
終了ページ 35
ISSN 0475-0071
言語 English
論文のバージョン publisher
NAID 120002308329
JaLCDOI 10.18926/14152
フルテキストURL Mem_Fac_Eng_39_1_52.pdf
著者 金森 克也| 東辻 千枝子| 鶴田 健二| 東辻 浩夫|
抄録 Thermal behavior of Coulomb clusters in a three dimensional confining potential is investigated by molecular dynamics simulations for system sizes of 1,000 to 20,288 ions. The specific heat of the system of shell-structured 20,000 ions is peaked almost at the same temperature as the system of bcc-structured 20,288 ions with much sharper structure for the latter. The diffusion coefficient and the peak to valley ratio of the two-dimensional pair distribution function on the outermost shell are obtained both as a function of temperature. The rotational movement of each shell in the system of 104 ions is observed.
出版物タイトル Memoirs of the Faculty of Engineering, Okayama University
発行日 2005-01
39巻
1号
開始ページ 52
終了ページ 55
ISSN 0475-0071
言語 English
論文のバージョン publisher
NAID 120002308445
JaLCDOI 10.18926/17831
フルテキストURL Mem_Fac_Eng_OU_43_22.pdf
著者 東辻 浩夫| Chai Hong| 東辻 千枝子| 鶴田 健二|
抄録 For the transfer of quantum information and the creation of entangled states, the application of tuned spin chains, systems of spins with the nearest-neighbor coupling tuned so as to give high efficiency, has been proposed and some examples of high performance have been given by several authors. In this article, the effect of deviations from tuned values and the effect of resultant asymmetry are investigated through numerical simulations and theoretical analyses. It is shown that there exists a system where the transfer efficiency is comparable with exactly tuned ones and, at the same time, robust to noises in the coupling constants. It is also shown that the effect of asymmetry on the efficiency of entanglement creation is of the second order when the asymmetry is small.
出版物タイトル Memoirs of the Faculty of Engineering, Okayama University
発行日 2009-01
43巻
開始ページ 22
終了ページ 26
ISSN 1349-6115
言語 English
論文のバージョン publisher
NAID 120002308966
JaLCDOI 10.18926/17829
フルテキストURL Mem_Fac_Eng_OU_43_16.pdf
著者 Kurose Tomoyuki| 鶴田 健二| 東辻 千枝子| 東辻 浩夫|
抄録 The finite-difference time-domain (FDTD) method has been applied to the calculation of the phonon band structure of two-dimensional (2D) phononic crystals, consisting of metal cylinders placed periodically in liquid. By comparing several combinations of materials for metal cylinder and liquid, we analyze the dependence of the band structures on sound speed and density of liquid media. Moreover, the negative refraction of the acoustic waves is observed at the interfaces between phononic crystal slab and the liquid. We find that an acoustic“lens effect”with the slab appears due to the negative refractions. The relationship between the focal intensity in the lens effect and the band structure is discussed.
出版物タイトル Memoirs of the Faculty of Engineering, Okayama University
発行日 2009-01
43巻
開始ページ 16
終了ページ 21
ISSN 1349-6115
言語 English
論文のバージョン publisher
NAID 120002308928