| 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 |
| 巻 | 35巻 |
| 号 | 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 | 10.18926/15358 |
|---|---|
| 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 |
| 巻 | 35巻 |
| 号 | 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 | 10.18926/14152 |
|---|---|
| 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 |
| 巻 | 39巻 |
| 号 | 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 | 10.18926/14150 |
|---|---|
| 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 |
| 巻 | 39巻 |
| 号 | 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 | 10.18926/14121 |
|---|---|
| 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 |
| 巻 | 40巻 |
| 号 | 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 | 10.18926/14120 |
|---|---|
| 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 |
| 巻 | 40巻 |
| 号 | 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 | 10.18926/14119 |
|---|---|
| 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 |
| 巻 | 40巻 |
| 号 | 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 | 10.18926/14061 |
|---|---|
| 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 |
| 巻 | 42巻 |
| 号 | 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 | 10.18926/14059 |
|---|---|
| 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 |
| 巻 | 42巻 |
| 号 | 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 | 10.18926/14058 |
|---|---|
| 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 |
| 巻 | 42巻 |
| 号 | 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 |