CMS seminar2006
Anomalous low-energy scattering in a Bose condensate
Prof. Yusuke Kato
【Date & Time】20 December 2006 (Wed), 3:30 pm - 5:00 pm
【Place】8F large seminar room, Sengen site
【Speaker】Prof. Yusuke Kato
【Affiliation】Graduate School of Arts and Sciences, the University of Tokyo
【Title】Anomalous low-energy scattering in a Bose condensate
【Abstract】
The superfluid (condensate) and normal (single particle excitation) components of a bose superfluid are suppose to be able to "penetrate" though each other, i.e. undergo relative motion without having to exchange momenta. Does this imply then that the excited particle will not be scattered off by a condensate even when the latter is spatially modulated by an impurity or a container's wall? The 1d version of this probem was undertaken by Kagan et al (2003) and Danshita et al (2005). Here we employ the Gross-Pitaevskii and Bogoluibov equations to study the 3d scattering problem of a particle excitation in the presence of both an impurity potential and a condensate spatially modulated by the potential. The results obtained provide a microsopic picture for the counterintuitive statement that the particle exciation is not scattered by the superfluid.
【Contact】Dr. Akihiro Tanaka
【Place】8F large seminar room, Sengen site
【Speaker】Prof. Yusuke Kato
【Affiliation】Graduate School of Arts and Sciences, the University of Tokyo
【Title】Anomalous low-energy scattering in a Bose condensate
【Abstract】
The superfluid (condensate) and normal (single particle excitation) components of a bose superfluid are suppose to be able to "penetrate" though each other, i.e. undergo relative motion without having to exchange momenta. Does this imply then that the excited particle will not be scattered off by a condensate even when the latter is spatially modulated by an impurity or a container's wall? The 1d version of this probem was undertaken by Kagan et al (2003) and Danshita et al (2005). Here we employ the Gross-Pitaevskii and Bogoluibov equations to study the 3d scattering problem of a particle excitation in the presence of both an impurity potential and a condensate spatially modulated by the potential. The results obtained provide a microsopic picture for the counterintuitive statement that the particle exciation is not scattered by the superfluid.
【Contact】Dr. Akihiro Tanaka
Proton shuttles and enzyme catalysis
Prof. M. L. Klein, FRS
【Date & Time】7 December 2006 (Thu), 3:30 pm - 5:00 pm
【Place】8F larger seminar room, Sengen site
【Speaker】Prof. M. L. Klein, FRS
【Affiliation】Director of Laboratory for Research on the Structure of Matter & Director of Center for Molecular Modeling, University of Pennsylvania
【Title】Proton shuttles and enzyme catalysis
【Abstract】
The talk will outline some recent attempts by my research group (www.cmm.upenn.edu) to employ the QM/MM Car-Parrinello based DFT methodology to some topical problems in enzyme catalysis. The mechanistic insights thus obtained are already useful to experimentalist notwithstanding the severe limitations on both the electonic structure aspects and the accessible time scales for phase space sampling.
【Contact】Dr. Yoshitaka Tateyama
【Place】8F larger seminar room, Sengen site
【Speaker】Prof. M. L. Klein, FRS
【Affiliation】Director of Laboratory for Research on the Structure of Matter & Director of Center for Molecular Modeling, University of Pennsylvania
【Title】Proton shuttles and enzyme catalysis
【Abstract】
The talk will outline some recent attempts by my research group (www.cmm.upenn.edu) to employ the QM/MM Car-Parrinello based DFT methodology to some topical problems in enzyme catalysis. The mechanistic insights thus obtained are already useful to experimentalist notwithstanding the severe limitations on both the electonic structure aspects and the accessible time scales for phase space sampling.
【Contact】Dr. Yoshitaka Tateyama
Simulation of liquid-crystal transition by an extended multicanonical method coupled with a first-principles calculation
Dr. Yoshihide Yoshimoto
【Date & Time】16 November 2006 (Thu), 3:30 pm - 5:00 pm
【Place】8F larger seminar room, Sengen site
【Speaker】Dr. Yoshihide Yoshimoto
【Affiliation】Institute for Solid State Physics, University of Tokyo
【Title】Simulation of liquid-crystal transition by an extended multicanonical method coupled with a first-principles calculation
【Abstract】
The multicanonical method is a powerful state survey algorithm that reduces relaxation time of a simulated system and determines its thermodynamic properties in a wide range of temperature. I have studied its combination with first-principles simulations of real materials. The seminar will present the recent results: the first is to extend the method to make it applicable to the liquid-crystal transition of silicon which tends to be overcooled like water. The second is to utilize the produced ensemble to determine a model interatomic potential from first-principles calculations conserving its thermodynamic properties to a maximum extent.
【Contact】Dr. Yoshitaka Tateyama
【Place】8F larger seminar room, Sengen site
【Speaker】Dr. Yoshihide Yoshimoto
【Affiliation】Institute for Solid State Physics, University of Tokyo
【Title】Simulation of liquid-crystal transition by an extended multicanonical method coupled with a first-principles calculation
【Abstract】
The multicanonical method is a powerful state survey algorithm that reduces relaxation time of a simulated system and determines its thermodynamic properties in a wide range of temperature. I have studied its combination with first-principles simulations of real materials. The seminar will present the recent results: the first is to extend the method to make it applicable to the liquid-crystal transition of silicon which tends to be overcooled like water. The second is to utilize the produced ensemble to determine a model interatomic potential from first-principles calculations conserving its thermodynamic properties to a maximum extent.
【Contact】Dr. Yoshitaka Tateyama
Deconfinement of vortices with continuously variable fractions of the unit flux quanta in two-gap superconductors
Dr. Jun Goryo
【Date & Time】2 November 2006 (Thu), 3:00 pm - 4:30 pm
【Place】8F large seminar room, Sengen site
【Speaker】Dr. Jun Goryo
【Affiliation】Department of Physics, Aoyama-Gakuin University
【Title】Deconfinement of vortices with continuously variable fractions of the unit flux quanta in two-gap superconductors
【Abstract】
We propose a new stage for observing a confinement-decofinement transition in the laboratory. In two-gap superconductors such as MgB2, there are two species of vortices, each carrying a continuously variable fraction of the unit flux quanta ψ0= hc/2e. The confined state of these two is the usual vortex which is stable in the low temperature region of the system under a certain magnetic field above Hc1. An entropy gain causes the two fractional vortices to be deconfined above a certain temperature. Here we see an analogy to quarks in a charged pion. We estimate the condition of the deconfinement by using parameters for a thin film of the typical two-gap superconductor MgB2.
【Contact】Dr. Akihiro Tanaka
【Place】8F large seminar room, Sengen site
【Speaker】Dr. Jun Goryo
【Affiliation】Department of Physics, Aoyama-Gakuin University
【Title】Deconfinement of vortices with continuously variable fractions of the unit flux quanta in two-gap superconductors
【Abstract】
We propose a new stage for observing a confinement-decofinement transition in the laboratory. In two-gap superconductors such as MgB2, there are two species of vortices, each carrying a continuously variable fraction of the unit flux quanta ψ0= hc/2e. The confined state of these two is the usual vortex which is stable in the low temperature region of the system under a certain magnetic field above Hc1. An entropy gain causes the two fractional vortices to be deconfined above a certain temperature. Here we see an analogy to quarks in a charged pion. We estimate the condition of the deconfinement by using parameters for a thin film of the typical two-gap superconductor MgB2.
【Contact】Dr. Akihiro Tanaka
Molecular Dynamics Simulation of formation process of single-walled carbon nanotubes
Dr. Yasushi Shibuta
【Date & Time】26 October 2006 (Thu), 2:30 pm - 4:00 pm
【Place】6F seminar room, Sengen site
【Speaker】Dr. Yasushi Shibuta
【Affiliation】Department of Materials Engineering, University of Tokyo
【Title】Molecular Dynamics Simulation of formation process of single-walled carbon nanotubes
【Abstract】
Several remarkable properties of Single-walled carbon nanotubes (SWNTs) are attractive such as a metal-semiconductor duality determined by its chirality and a high thermal conductivity. In addition to initially developed laser-furnace technique by Smalley’s group in 1996, a catalytic chemical vapor deposition (CCVD) method enabled the large-scale production of SWNT. However, the diameter and chirality control is still unrealistic. The formation mechanism of SWNT has been widely discussed since its discovery. However, it is difficult to reproduce the entire formation process of SWNTs due to computational limits on the system size and time scale.
Hence, the formation process of SWNTs is studied by molecular dynamics simulation using novel many-body potential functions between carbon atoms and catalytic metal atoms constructed by fitting binding energies from DFT calculation.
【Contact】Dr. Machiko Ode
【Place】6F seminar room, Sengen site
【Speaker】Dr. Yasushi Shibuta
【Affiliation】Department of Materials Engineering, University of Tokyo
【Title】Molecular Dynamics Simulation of formation process of single-walled carbon nanotubes
【Abstract】
Several remarkable properties of Single-walled carbon nanotubes (SWNTs) are attractive such as a metal-semiconductor duality determined by its chirality and a high thermal conductivity. In addition to initially developed laser-furnace technique by Smalley’s group in 1996, a catalytic chemical vapor deposition (CCVD) method enabled the large-scale production of SWNT. However, the diameter and chirality control is still unrealistic. The formation mechanism of SWNT has been widely discussed since its discovery. However, it is difficult to reproduce the entire formation process of SWNTs due to computational limits on the system size and time scale.
Hence, the formation process of SWNTs is studied by molecular dynamics simulation using novel many-body potential functions between carbon atoms and catalytic metal atoms constructed by fitting binding energies from DFT calculation.
【Contact】Dr. Machiko Ode
The Coulomb interactions and the chemical hardness
Dr. Taizo Sasaki
【Date & Time】12 October 2006 (Thu), 3:30 pm - 5:00 pm
【Place】6F seminar room, Sengen site
【Speaker】Dr. Taizo Sasaki
【Affiliation】First-Principles Simulation group (II), NIMS-CMSC
【Title】The Coulomb interactions and the chemical hardness
【Abstract】
The chemical hardness is the concept that assists obtaining an idea of the probability of chemical bond between atoms and/or molecules. The quantity representing it is called the absolute hardness, defined as η= (I-A)/2, where I and A are the ionization energy and the electron affinity, respectively. It has been considered that the absolute hardness η for the species with the open-shell structure characterizes the strength of the Coulomb interaction between electrons. In the solid state physics, η has been regarded as Hubbard's U (= 2η). Recently, we have found that a major part of η comes from the electron-nucleus term and the contribution of the electron-electron interaction is negative.
【Contact】Dr. Yoshitaka Tateyama
【Place】6F seminar room, Sengen site
【Speaker】Dr. Taizo Sasaki
【Affiliation】First-Principles Simulation group (II), NIMS-CMSC
【Title】The Coulomb interactions and the chemical hardness
【Abstract】
The chemical hardness is the concept that assists obtaining an idea of the probability of chemical bond between atoms and/or molecules. The quantity representing it is called the absolute hardness, defined as η= (I-A)/2, where I and A are the ionization energy and the electron affinity, respectively. It has been considered that the absolute hardness η for the species with the open-shell structure characterizes the strength of the Coulomb interaction between electrons. In the solid state physics, η has been regarded as Hubbard's U (= 2η). Recently, we have found that a major part of η comes from the electron-nucleus term and the contribution of the electron-electron interaction is negative.
【Contact】Dr. Yoshitaka Tateyama
New Trends in Quantum Chemical Calculations
Prof. Hiromi Nakai
【Date & Time】12 July 2006 (Wed), 3:30 pm - 5:00 pm
【Place】8F large seminar room, Sengen site
【Speaker】Professor Hiromi Nakai
【Affiliation】Faculty of Science Engineering, Waseda University
【Title】New Trends in Quantum Chemical Calculations
【Abstract】
The seminar presents the historical background of quantum chemical calculations based on the molecular orbital (MO) method and density functional theory (DFT), and gives novel theoretical and methodological treatments developed by Nakai's research group. The first topic is the proposal of energy density analysis (EDA), which enables us to partition the total energy of the system obtained by ab initio MO or DFT calculation into atomic contributions. The second is the development of nuclear orbital plus molecular orbital (NOMO) theory, which can give the nuclear and electronic wave functions simultaneously without the Born-Oppenheimer (BO) approximation.
【Contact】Dr. Takahisa Ohno
【Place】8F large seminar room, Sengen site
【Speaker】Professor Hiromi Nakai
【Affiliation】Faculty of Science Engineering, Waseda University
【Title】New Trends in Quantum Chemical Calculations
【Abstract】
The seminar presents the historical background of quantum chemical calculations based on the molecular orbital (MO) method and density functional theory (DFT), and gives novel theoretical and methodological treatments developed by Nakai's research group. The first topic is the proposal of energy density analysis (EDA), which enables us to partition the total energy of the system obtained by ab initio MO or DFT calculation into atomic contributions. The second is the development of nuclear orbital plus molecular orbital (NOMO) theory, which can give the nuclear and electronic wave functions simultaneously without the Born-Oppenheimer (BO) approximation.
【Contact】Dr. Takahisa Ohno
Topological nature of anomalous Hall effect, dissipationless charge
-transfer through insulating media, and magneto-electric effect
Dr. Shigeki Onoda
【Date & Time】29 June 2006 (Thu), 3:30 pm - 5:00 pm
【Place】8F large seminar room, Sengen site
【Speaker】Dr. Shigeki Onoda
【Affiliation】Tokura Spin Superstructure Project, ERATO, JST
【Title】Topological nature of anomalous Hall effect, dissipationless charge-transfer through insulating media, and magneto-electric effect
【Abstract】
The topology of the momentum/parameter-space lies at the heart of the quantum Hall effect and the Berry-phase theory of macroscopic electric polarization, as well as a host of other condensed matter phenomena which had not been fully appreciated till recently. In this talk I will discuss from this perspective the following topics (1) the anomalous Hall effect in ferromagnets (2) adiabatic charge pumping in ionic dimer insulators (3) the toroidal moment and magneto-electric
【Contact】Dr. Akihiro Tanaka
【Place】8F large seminar room, Sengen site
【Speaker】Dr. Shigeki Onoda
【Affiliation】Tokura Spin Superstructure Project, ERATO, JST
【Title】Topological nature of anomalous Hall effect, dissipationless charge-transfer through insulating media, and magneto-electric effect
【Abstract】
The topology of the momentum/parameter-space lies at the heart of the quantum Hall effect and the Berry-phase theory of macroscopic electric polarization, as well as a host of other condensed matter phenomena which had not been fully appreciated till recently. In this talk I will discuss from this perspective the following topics (1) the anomalous Hall effect in ferromagnets (2) adiabatic charge pumping in ionic dimer insulators (3) the toroidal moment and magneto-electric
【Contact】Dr. Akihiro Tanaka
Ultrafast dynamics of many-body interacting complexes
Dr. JaeDong Lee
【Date & Time】15 June 2006 (Thu), 3:30 pm - 5:00 pm
【Place】6F seminar room, Sengen site
【Speaker】Dr. JaeDong Lee
【Affiliation】NIMS-ICYS
Ultrafast dynamics of many-body interacting complexes
【Abstract】
We are strongly motivated to study the ultrafast dynamics of many-body interacting systems due to several reasons; (i) it gives new physics or new science, (ii) the controlled dynamics of the functionally smart systems in the ultrafast time range has the huge potential applicability, (iii) it can give the fundamental cornerstone for the field of "photodynamics". In the experimental side, thanks to an advancement of the ultrashort pulsed laser, it has been possible to study the ultrafast phenomena occurring within picoseconds or femtoseconds. On the other hand, in the theoretical side, it is true that a proper theoretical formulation is still lacking. Accordingly, we suggest the formalism starting from an idea of the real-time diagonalization within the many-body Hilbert space. We demonstrate that the formalism is quite successful and promising by introducing a few examples; (i) Birth of quasiparticles in a semiconductor and related ultrafast phenomena, (ii) Controlled propagation of molecular polarization, (iii) Photoinduced insulator-metal transition of one-dimensional Mott insulator. Besides those, if time is allowed, we introduce further issues related to intriguing ultrafast phenomena.
【Contact】Dr. Junichi Inoue
【Place】6F seminar room, Sengen site
【Speaker】Dr. JaeDong Lee
【Affiliation】NIMS-ICYS
Ultrafast dynamics of many-body interacting complexes
【Abstract】
We are strongly motivated to study the ultrafast dynamics of many-body interacting systems due to several reasons; (i) it gives new physics or new science, (ii) the controlled dynamics of the functionally smart systems in the ultrafast time range has the huge potential applicability, (iii) it can give the fundamental cornerstone for the field of "photodynamics". In the experimental side, thanks to an advancement of the ultrashort pulsed laser, it has been possible to study the ultrafast phenomena occurring within picoseconds or femtoseconds. On the other hand, in the theoretical side, it is true that a proper theoretical formulation is still lacking. Accordingly, we suggest the formalism starting from an idea of the real-time diagonalization within the many-body Hilbert space. We demonstrate that the formalism is quite successful and promising by introducing a few examples; (i) Birth of quasiparticles in a semiconductor and related ultrafast phenomena, (ii) Controlled propagation of molecular polarization, (iii) Photoinduced insulator-metal transition of one-dimensional Mott insulator. Besides those, if time is allowed, we introduce further issues related to intriguing ultrafast phenomena.
【Contact】Dr. Junichi Inoue
Quantum Transport Properties in Nano-scale materials
Dr. Hisashi Kondo
【Date & Time】25 May 2006 (Thu), 3:30 pm - 5:00 pm
【Place】6F seminar room, Sengen site
【Speaker】Dr. Hisashi Kondo
【Affiliation】Inst. for Industrial Science, Univ. of Tokyo/First-Principles Simulation group (I), NIMS-CMSC
【Title】Quantum Transport Properties in Nano-scale materials
【Abstract】
Major topics in nanotechnology include studies on electron transport properties for nano-scale materials bridging metal electrodes. One of the fundamental issues in the study of molecular electronics is to understand how the transport properties of the molecular device are determined by its atomic and electronic structures. We have studied the transport properties of the junction system of the single molecule bridging Au(111) electrodes by using the non-equilibrium Green's function method. In this talk, the method of calculation and some examples of its application will be presented.
【Contact】Dr. Jun Nara
【Place】6F seminar room, Sengen site
【Speaker】Dr. Hisashi Kondo
【Affiliation】Inst. for Industrial Science, Univ. of Tokyo/First-Principles Simulation group (I), NIMS-CMSC
【Title】Quantum Transport Properties in Nano-scale materials
【Abstract】
Major topics in nanotechnology include studies on electron transport properties for nano-scale materials bridging metal electrodes. One of the fundamental issues in the study of molecular electronics is to understand how the transport properties of the molecular device are determined by its atomic and electronic structures. We have studied the transport properties of the junction system of the single molecule bridging Au(111) electrodes by using the non-equilibrium Green's function method. In this talk, the method of calculation and some examples of its application will be presented.
【Contact】Dr. Jun Nara
Anisotropy of Upper Critical Fields of conventional superconductivity
: Effects of Fermi Surface Geometry
Dr. Masao Arai
【Date & Time】11 May 2006 (Thu), 3:30 pm - 5:00 pm
【Place】6F seminar room, Sengen site
【Speaker】Dr. Masao Arai
【Affiliation】First-Principles Simulation group (II), NIMS-CMSC
【Title】Anisotropy of Upper Critical Fields of conventional superconductivity: Effects of Fermi Surface Geometry
【Abstract】
From the early stage of research on classical type-II superconductors, it has been recognized that the detailed anisotropy of Fermi surface has significant effects on H$_{c2}$. Recently, we have derived an H$_{c2}$ equation applicable to low-symmetry crystals, including Fermi surface anisotropy, gap anisotropy and impurity scatterings completely [T. Kita and M. Arai, Phys. Rev.B 70, 224522 (2004)]. By applying this equation to Fermi surfaces obtained from non-empirical calculations, we computed the H$_{c2}$ for Nb, NbSe$_2$, and MgB$_2$ within weak-coupling theory. It is found that the calculated H$_{c2}$ curves are in good agreement with the experimentally observed temperature and field angle dependences for Nb and NbSe$_2$.
【Contact】Dr. Kazuaki Kobayashi
【Place】6F seminar room, Sengen site
【Speaker】Dr. Masao Arai
【Affiliation】First-Principles Simulation group (II), NIMS-CMSC
【Title】Anisotropy of Upper Critical Fields of conventional superconductivity: Effects of Fermi Surface Geometry
【Abstract】
From the early stage of research on classical type-II superconductors, it has been recognized that the detailed anisotropy of Fermi surface has significant effects on H$_{c2}$. Recently, we have derived an H$_{c2}$ equation applicable to low-symmetry crystals, including Fermi surface anisotropy, gap anisotropy and impurity scatterings completely [T. Kita and M. Arai, Phys. Rev.B 70, 224522 (2004)]. By applying this equation to Fermi surfaces obtained from non-empirical calculations, we computed the H$_{c2}$ for Nb, NbSe$_2$, and MgB$_2$ within weak-coupling theory. It is found that the calculated H$_{c2}$ curves are in good agreement with the experimentally observed temperature and field angle dependences for Nb and NbSe$_2$.
【Contact】Dr. Kazuaki Kobayashi
Introduction of phase-field method and its application examples
Dr. Machiko Ode
【Date & Time】12 April 2006 (Wed), 3:30 pm - 5:00 pm
【Place】6F seminar room, Sengen site
【Speaker】Dr. Machiko Ode
【Affiliation】Particle Simulation & Thermodynamics group, NIMS-CMSC
【Title】Introduction of phase-field method and its application examples
【Abstract】
Over the last decade, the phase-field approach has been developed extensively to model solidification, solid-solid transformation, grain growth and so on. In the phase-field method, phase-field variable is introduced to describe the state (solid or liquid phase, for example) in a material. The interfacial regions involve continuous but highly localized variations of the phase-field. By incorporating the phase-field variable into the phase-field equation, thermal conduction equation and diffusion equation, the change in the phase distribution, i.e. complex microstructure evolution in a material can be solved without tracking the interface. An overview of the phase-field method will be presented, together with application examples.
【Contact】Dr. Toshiyuki Koyama
【Place】6F seminar room, Sengen site
【Speaker】Dr. Machiko Ode
【Affiliation】Particle Simulation & Thermodynamics group, NIMS-CMSC
【Title】Introduction of phase-field method and its application examples
【Abstract】
Over the last decade, the phase-field approach has been developed extensively to model solidification, solid-solid transformation, grain growth and so on. In the phase-field method, phase-field variable is introduced to describe the state (solid or liquid phase, for example) in a material. The interfacial regions involve continuous but highly localized variations of the phase-field. By incorporating the phase-field variable into the phase-field equation, thermal conduction equation and diffusion equation, the change in the phase distribution, i.e. complex microstructure evolution in a material can be solved without tracking the interface. An overview of the phase-field method will be presented, together with application examples.
【Contact】Dr. Toshiyuki Koyama
The ALPS project: Open source software for simulation of quantum lattice models
Professor Synge Todo
【Date & Time】23 February 2006 (Thu), 3:00 pm - 4:30 pm
【Place】8F large seminar room, Sengen site
【Speaker】Professor Synge Todo
【Affiliation】Department of Applied Physics, University of Tokyo
【Title】The ALPS project: Open source software for simulation of quantum lattice models
【Abstract】
The ALPS (Algorithm and Libraries for Physics Simulations) project is an international collaboration to develop open source software for the simulation of strongly correlated quantum lattice models such as quantum magnets and electron systems. Development is focused on common XML data formats, on the libraries as a foundation of large-scale parallel simulation codes, and on the fully-featured application programs based on the state-of-art algorithms. In this seminar, after a brief introduction on recent developments in computer science, such as generic programming in C++ and XML, we will present the details about the ALPS libraries (lattice, model, etc) as well as the ALPS applications (exact diagonalization, quantum Monte Carlo, etc). We will also present the results of our recent Monte Carlo simulations, using the ALPS libraries, on quantum spin systems.
【Contact】Dr. Masanori Kohno
【Place】8F large seminar room, Sengen site
【Speaker】Professor Synge Todo
【Affiliation】Department of Applied Physics, University of Tokyo
【Title】The ALPS project: Open source software for simulation of quantum lattice models
【Abstract】
The ALPS (Algorithm and Libraries for Physics Simulations) project is an international collaboration to develop open source software for the simulation of strongly correlated quantum lattice models such as quantum magnets and electron systems. Development is focused on common XML data formats, on the libraries as a foundation of large-scale parallel simulation codes, and on the fully-featured application programs based on the state-of-art algorithms. In this seminar, after a brief introduction on recent developments in computer science, such as generic programming in C++ and XML, we will present the details about the ALPS libraries (lattice, model, etc) as well as the ALPS applications (exact diagonalization, quantum Monte Carlo, etc). We will also present the results of our recent Monte Carlo simulations, using the ALPS libraries, on quantum spin systems.
【Contact】Dr. Masanori Kohno
First-principles calculations for the initial stages of the oxidation on Si(001) surfaces
Prof. Byung Deok Yu
【Date & Time】9 February 2006 (Thu), 3:30 pm - 5:00 pm
【Place】6F seminar room, Sengen site
【Speaker】Professor Byung Deok Yu
【Affiliation】Department of Physics, University of Seoul
【Title】First-principles calculations for the initial stages of the oxidation on Si(001) surfaces
【Abstract】
The oxidation of silicon surfaces has attracted much attention as one of the most important processes in current and future Si technology. Particularly, the control of the initial reactions of oxygen to Si surfaces on an atomic scale is an important issue that must be addressed for more stable and better-functioning Si devices.
In this talk, I will present possible initial oxidation structures on flat terraces and at single-layer steps of Si(001) using first-principles total-energy and electronic-structure calculations based on the density-functional theory (DFT). For various oxidation models, the supercell contains a different number of oxygen atoms. Here, I will explain how such a system can be treated in the thermodynamic limit. More detailed information on the electronic properties, such as the local density of states and the scanning tunneling microscopy images, were also determined by the first-principles calculations. The characteristic features that were found therein are discussed and compared to the experimental results. Finally, I will briefly mention our plan to further understand the initial oxidation reactions to Si surfaces.
【Contact】Dr. Takahisa Ohno
【Place】6F seminar room, Sengen site
【Speaker】Professor Byung Deok Yu
【Affiliation】Department of Physics, University of Seoul
【Title】First-principles calculations for the initial stages of the oxidation on Si(001) surfaces
【Abstract】
The oxidation of silicon surfaces has attracted much attention as one of the most important processes in current and future Si technology. Particularly, the control of the initial reactions of oxygen to Si surfaces on an atomic scale is an important issue that must be addressed for more stable and better-functioning Si devices.
In this talk, I will present possible initial oxidation structures on flat terraces and at single-layer steps of Si(001) using first-principles total-energy and electronic-structure calculations based on the density-functional theory (DFT). For various oxidation models, the supercell contains a different number of oxygen atoms. Here, I will explain how such a system can be treated in the thermodynamic limit. More detailed information on the electronic properties, such as the local density of states and the scanning tunneling microscopy images, were also determined by the first-principles calculations. The characteristic features that were found therein are discussed and compared to the experimental results. Finally, I will briefly mention our plan to further understand the initial oxidation reactions to Si surfaces.
【Contact】Dr. Takahisa Ohno
The Avogadoro Challenge
Professor Nobuyasu Ito
【Date & Time】25 January 2006 (Wed), 3:00 pm - 5:00 pm
【Place】8F large seminar room, Sengen site
【Speaker】Professor Nobuyasu Ito
【Affiliation】Department of Applied Physics, University of Tokyo
【Title】The Avogadoro Challenge
【Abstract】
The aim of the computing statistical physics is to elucidate macroscopic phenomena based on nanoscopic dynamics. Now the equilibrium phases and transitions have been mostly conquered, and current targets are further complex and exotic equilibrium states and materials. Furthermore, linear nonequilibrium transport phenomena, which had been a mystery for statistical physicists for more than half a century, are finally connected with the nanoscale dynamics simulationally. For these studies, Monte Carlo simulation of lattice spin systems and particle dynamics simulation have been used. Now the Earth Simulator can analyze Ising model on 30003 cubic lattices with the speed of 26.7 T (1012) update per second, and this simulation reaches mesoscopic scale in space and time directions. Computer simulation scale has been growing ten times larger at every four years, and we are reaching Avogadoro scale simulation with future 10PFlops machines. Then redefinition of statistical physics, which had formulated regarding that the Avogadoro number is almost infinity, will bring a new realm of sciences and technologies.
【Contact】Dr. Yoshihiko Nonomura
【Place】8F large seminar room, Sengen site
【Speaker】Professor Nobuyasu Ito
【Affiliation】Department of Applied Physics, University of Tokyo
【Title】The Avogadoro Challenge
【Abstract】
The aim of the computing statistical physics is to elucidate macroscopic phenomena based on nanoscopic dynamics. Now the equilibrium phases and transitions have been mostly conquered, and current targets are further complex and exotic equilibrium states and materials. Furthermore, linear nonequilibrium transport phenomena, which had been a mystery for statistical physicists for more than half a century, are finally connected with the nanoscale dynamics simulationally. For these studies, Monte Carlo simulation of lattice spin systems and particle dynamics simulation have been used. Now the Earth Simulator can analyze Ising model on 30003 cubic lattices with the speed of 26.7 T (1012) update per second, and this simulation reaches mesoscopic scale in space and time directions. Computer simulation scale has been growing ten times larger at every four years, and we are reaching Avogadoro scale simulation with future 10PFlops machines. Then redefinition of statistical physics, which had formulated regarding that the Avogadoro number is almost infinity, will bring a new realm of sciences and technologies.
【Contact】Dr. Yoshihiko Nonomura