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 10.18926/14059
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 10.18926/14061
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 10.18926/14119
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 10.18926/14120
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 10.18926/14121
フルテキストURL Mem_Fac_Eng_OU_40_1_40.pdf
著者 三宅 隆| 東辻 千枝子| 鶴田 健二| 東辻 浩夫|
抄録 The electron system of arbitrary degeneracy can be mapped onto a classical system where electrons of the same spin are assigned an additional interaction and the effect of degeneracy is taken into account through an imaginative temperature. We apply this method to electrons in quantum dots modeled as two-dimensional electron liquid confined in a finite domain by a harmonic potential. We analyze distribution functions by molecular dynamics instead of solving integral equations which are not so useful in the case without translational invariance.
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 40
終了ページ 43
ISSN 0475-0071
言語 English
論文のバージョン publisher
NAID 120002308268
JaLCDOI 10.18926/14150
フルテキストURL Mem_Fac_Eng_39_1_46.pdf
著者 門野 恵典| 東辻 千枝子| 鶴田 健二| 東辻 浩夫|
抄録 We present a real-space, polynomial-expansion approach to electron dynamics in nanostructured semiconductors. The Chebyshev expansion method is employed for efficient calculation of timeevolution of single-electron wave function. Details of the formulation are described. The method is applied to the electron transport in nanostructured semiconductors such as Si nanowires. The mean-square displacement and diffusivity of electron in Si chains are obtained as functions of length of the chains. The results show clearly ballistic behavior of electron in the pure Si chain.
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 46
終了ページ 51
ISSN 0475-0071
言語 English
論文のバージョン publisher
NAID 120002308231
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 10.18926/15358
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 10.18926/15361
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 10.18926/17826
フルテキストURL Mem_Fac_Eng_OU_43_8.pdf
著者 Umeda Ryosuke| 東辻 千枝子| 鶴田 健二| 東辻 浩夫|
抄録 Metamaterial which has negative permittivity and permeability is investigated via computer simulations. Effects of the nanostructure on dielectric and magnetic properties of the material are taken into account by introducing the Drude-Lorentz model in the materials dispersion. We include multi-band process in the dielectric response in order to reproduce accurately experimental values of bulk Au thin film. Size effect on the dispersion is examined by comparing the model with that of a noble metal particle. Based on the dispersion model constructed, we analyze the electromagnetic response of nanostructured metamaterials to evanescent waves at microwave and optical frequencies via finite-difference time-domain simulatioins on parallel computer. A re- focusing and an amplification of the evanescent waves propagating through a metamaterial, consisting of metal slab/vacuum stacking, is demonstrated for the frequencies of 30GHz and 744THz.
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 8
終了ページ 15
ISSN 1349-6115
言語 English
論文のバージョン publisher
NAID 120002308833
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
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 10.18926/19671
フルテキストURL Mem_Fac_Eng_OU_33_2_51.pdf
著者 東辻 浩夫| 鶴田 健二| 東辻 千枝子|
抄録 Density functional molecular dynamics method is applied to hydrogen plasma in the domain of liquid metallic hydrogen. Tentative results for the proton-proton pair distribution function and the electron-proton pair distribution function are obtained. It is shown that with the increase of the parameter γ(s), we have increasingly strong screening of proton charge by electrons and the decrease of electron density in the domain between protons.
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 51
終了ページ 59
ISSN 0475-0071
言語 English
論文のバージョン publisher
NAID 120002309192
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 10.18926/19674
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 10.18926/19953
フルテキストURL Mem_Fac_Eng_OU_44_1.pdf
著者 Nagai Shinji| Umeda Ryosuke| 鶴田 健二|
抄録 In this paper, we investigate a light-confinement phenomenon in the structure which has triangular latice composed of Double NeGative Metamaterial (DNGM). In geometrical optics consideration, this structure is expected to confine lights completely by sequential refractions in the structure. We demonstrate it by using the two dimensional finite-difference time-domain simulations. We introduce Drude-Lorentz model for dielectric and magnetic dispersion of the material at optical frequencies. We analyze quantitatively the effects of energy loss in the DNGM on the light-confinement efficiency.
出版物タイトル Memoirs of the Faculty of Engineering, Okayama University
発行日 2010-01
44巻
開始ページ 1
終了ページ 6
ISSN 1349-6115
言語 English
論文のバージョン publisher
NAID 120002309117
JaLCDOI 10.18926/19954
フルテキストURL Mem_Fac_Eng_OU_44_7.pdf
著者 Maetani Noriaki| Kurose Tomoyuki| 鶴田 健二|
抄録 The lens effect of acoustic waves in a two-dimensional (2D) phononic crystal is studied by numerical simulation based on the finite-difference time-domain (FDTD) method. We calculate the phonon band structure of 2D phononic crystals, consisting of metal cylinders placed periodically in water. Lens effect is observed by the negative refraction of acoustic waves, which results in refocusing of the waves at the point outside the crystal. To increase the focal intensity, we introduce a 2D phononic crystal shield with a different composition of material, which returns the incident waves back to the lens via the perfect reflection. Also, the dependence on filling fraction of metal in the crystal is studied.
出版物タイトル Memoirs of the Faculty of Engineering, Okayama University
発行日 2010-01
44巻
開始ページ 7
終了ページ 12
ISSN 1349-6115
言語 English
論文のバージョン publisher
NAID 120002309019
著者 Totsuji, Hiroo| Totsuji, Chieko| Ogawa, Takafumi| Tsuruta, Kenji|
発行日 2005-4
出版物タイトル Physical Review E
71巻
4号
資料タイプ 学術雑誌論文
著者 Totsuji, Hiroo| Ogawa, Takafumi| Totsuji, Chieko| Tsuruta, Kenji|
発行日 2005-9
出版物タイトル Physical Review E
72巻
3号
資料タイプ 学術雑誌論文