CMSセミナー2013
Ab initio studies of molecule-metal interfaces for molecular electronics and spintronics
Mr. Martin Callsen
【Date & Time】16 December 2013 (Mon.) 15:30 - 16:30
【Place】4F seminar room (#431-2), MANA bldg., Namiki site
【Speaker】Mr. Martin Callsen
【Affiliation】Peter Grunberg Inst. (PGI-1) & Inst. for Advanced Simulation (IAS-1), Forschungszentrum Julich and JARA, Julich, Germany
【Title】Ab initio studies of molecule-metal interfaces for molecular electronics and spintronics
【Abstract】
I will present DFT calculations on hybrid metal-organic model systems for spintronics applications. Recently designing molecular switches either by redox reactions or by conformational changes has been pursued in molecular electronics. Cyclooctatetraene (COT) adsorbed on different noble metal substrates has been investigated as a possible candidate for a conformational switch. The role of charge states which change the conformation of COT in the gas phase is taken by the different strength of hybridization between the COT molecule and the surface. As a candidate for a molecular spintronics device we studied the adsorption of the prototypical, biplanar [2,2]paracyclophane molecule on the Fe/W(110) surface, which locally increases the strength of the magnetic exchange interaction between the Fe atoms directly binding to the molecule[1]. The observed magnetic hardening effect leads to the creation of a local molecule mediated magnetic unit with a stable magnetization direction and an enhanced barrier for the magnetization switching as compared to the clean surface.
[1] M. Callsen, et al., Phys. Rev. Lett. 111, 106805 (2013).
【Contact】Dr. Ikutaro Hamada(濱田幾太郎)
【Place】4F seminar room (#431-2), MANA bldg., Namiki site
【Speaker】Mr. Martin Callsen
【Affiliation】Peter Grunberg Inst. (PGI-1) & Inst. for Advanced Simulation (IAS-1), Forschungszentrum Julich and JARA, Julich, Germany
【Title】Ab initio studies of molecule-metal interfaces for molecular electronics and spintronics
【Abstract】
I will present DFT calculations on hybrid metal-organic model systems for spintronics applications. Recently designing molecular switches either by redox reactions or by conformational changes has been pursued in molecular electronics. Cyclooctatetraene (COT) adsorbed on different noble metal substrates has been investigated as a possible candidate for a conformational switch. The role of charge states which change the conformation of COT in the gas phase is taken by the different strength of hybridization between the COT molecule and the surface. As a candidate for a molecular spintronics device we studied the adsorption of the prototypical, biplanar [2,2]paracyclophane molecule on the Fe/W(110) surface, which locally increases the strength of the magnetic exchange interaction between the Fe atoms directly binding to the molecule[1]. The observed magnetic hardening effect leads to the creation of a local molecule mediated magnetic unit with a stable magnetization direction and an enhanced barrier for the magnetization switching as compared to the clean surface.
[1] M. Callsen, et al., Phys. Rev. Lett. 111, 106805 (2013).
【Contact】Dr. Ikutaro Hamada(濱田幾太郎)
Computational Modeling of New Materials for Electrochemical Solar-to-Fuel Energy Conversion
Dr. Stefano Fabris
【Date & Time】23 August 2013 (Fri.) 15:45 - 16:30
【Place】4F seminar room (#431-2), MANA bldg., Namiki site
【Speaker】Dr. Stefano Fabris
【Affiliation】CNR-IOM DEMOCRITOS and SISSA, Trieste, Italy
【Title】Computational Modeling of New Materials for Electrochemical Solar-to-Fuel Energy Conversion
【Abstract】
The conversion and storage of solar energy into chemical fuels rely on finding novel catalytic materials for the electrochemical splitting of water. These catalysts should be stable, inexpensive, efficient and easily integrable in photovoltaic units. In this talk I will present an overview of how state-of-the-art computational modeling can provide the missing insight into the structure and function of some of the most promising candidate anodic materials for artificial leaf technologies.
In particular I will address three paradigmatic water-oxidation class of catalysts: i) Heterogeneous amorphous cobalt-phosphate (Co-Pi) nanoparticles based on earth-abundant elements. ii) Homogeneous molecular complexes based on single and multiple active metal centers, and iii) hybrid nanostructures consisting of molecular catalysts bound to functionalized conducting substrates. The calculated results allow for rationalizing the available experimental data and identify the origins of the high reactivity and stability of these novel catalysts.
【Contact】Dr. Yoshitaka Tateyama(館山佳尚)
【Place】4F seminar room (#431-2), MANA bldg., Namiki site
【Speaker】Dr. Stefano Fabris
【Affiliation】CNR-IOM DEMOCRITOS and SISSA, Trieste, Italy
【Title】Computational Modeling of New Materials for Electrochemical Solar-to-Fuel Energy Conversion
【Abstract】
The conversion and storage of solar energy into chemical fuels rely on finding novel catalytic materials for the electrochemical splitting of water. These catalysts should be stable, inexpensive, efficient and easily integrable in photovoltaic units. In this talk I will present an overview of how state-of-the-art computational modeling can provide the missing insight into the structure and function of some of the most promising candidate anodic materials for artificial leaf technologies.
In particular I will address three paradigmatic water-oxidation class of catalysts: i) Heterogeneous amorphous cobalt-phosphate (Co-Pi) nanoparticles based on earth-abundant elements. ii) Homogeneous molecular complexes based on single and multiple active metal centers, and iii) hybrid nanostructures consisting of molecular catalysts bound to functionalized conducting substrates. The calculated results allow for rationalizing the available experimental data and identify the origins of the high reactivity and stability of these novel catalysts.
【Contact】Dr. Yoshitaka Tateyama(館山佳尚)
Microscopic understanding of solid-aqueous interfaces based on long-time first-principles MD calculations
Prof. Kazuto Akagi / 赤木和人氏
【Date & Time】31 May 2013 (Fri.) 16:15-17:00
【Place】Auditorium, 1F, WPI-MANA bldg., Namiki site
【Speaker】Prof. Kazuto Akagi / 赤木和人氏
【Affiliation】WPI-AIMR, Tohoku University / 東北大学 WPI-AIMR
【Title】Microscopic understanding of solid-aqueous interfaces based on long-time first-principles MD calculations
【Abstract】
The first-principles molecular dynamics (FPMD) method is a powerful tool to obtain a microscopic picture of the solid-liquid interface at which chemical environment is not trivial. First, structure and dynamics of a NaClaq-Au(111) interface system is discussed based on long time (~100ps) FPMD calculations. We will see specific adsorption of anion comes from a few of competitive factors. Next, behavior of H+ and OH－ at the interfacial region is discussed from the viewpoint of defects in a hydrogen-bond network.
I will show how their behavior changes depending on the hydrogen coverage of H2SO4-Pt(111) interfaces. Through this talk, I will also introduce suggestive information (e.g. hierarchy of the time scale) can be obtained from the analysis on higher order structure of a hydrogen-bond network.
【Contact】Dr. Yoshitaka Tateyama(館山佳尚)
【Place】Auditorium, 1F, WPI-MANA bldg., Namiki site
【Speaker】Prof. Kazuto Akagi / 赤木和人氏
【Affiliation】WPI-AIMR, Tohoku University / 東北大学 WPI-AIMR
【Title】Microscopic understanding of solid-aqueous interfaces based on long-time first-principles MD calculations
【Abstract】
The first-principles molecular dynamics (FPMD) method is a powerful tool to obtain a microscopic picture of the solid-liquid interface at which chemical environment is not trivial. First, structure and dynamics of a NaClaq-Au(111) interface system is discussed based on long time (~100ps) FPMD calculations. We will see specific adsorption of anion comes from a few of competitive factors. Next, behavior of H+ and OH－ at the interfacial region is discussed from the viewpoint of defects in a hydrogen-bond network.
I will show how their behavior changes depending on the hydrogen coverage of H2SO4-Pt(111) interfaces. Through this talk, I will also introduce suggestive information (e.g. hierarchy of the time scale) can be obtained from the analysis on higher order structure of a hydrogen-bond network.
【Contact】Dr. Yoshitaka Tateyama(館山佳尚)
Impact of adsorbates on water-surface interaction: A density functional theory study
Dr. Ikutaro Hamada / 濱田幾太郎氏
【Date & Time】25 February 2013 (Mon.) 16:00-17:00
【Place】4F room 409/410, Collaborative Bldg., Namiki site
【Speaker】Dr. Ikutaro Hamada / 濱田幾太郎氏
【Affiliation】WPI-AIMR, Tohoku University / 東北大学 WPI-AIMR
【Title】Impact of adsorbates on water-surface interaction: A density functional theory study
【Abstract】
Interaction of water with a surface has been studied extensively, because it has implications for various fields ranging from daily life to science and technology, including wetting, lubrication, corrosion, heterogeneous catalysis, and electrochemistry. In many theoretical studies of water on metal surfaces, only clean surfaces were considered, and less attention has been paid for the interaction of water with adsorbates and that between adsorbates. However, these interactions are particularly important in electrochemistry, as they are directly related to heterogeneous catalytic reactions at electrode/electrolyte interfaces. In this talk, I will introduced density functional theory study of interactions between water and metal surfaces with and without adsorbate and discuss how the specific adsorbates modify the water-surface interactions. I will discuss the implication to the electrochemistry and how the surface science approach helps to understand the complex electrochemical interfaces.
【Contact】Dr. Yoshitaka Tateyama(館山佳尚)
【Place】4F room 409/410, Collaborative Bldg., Namiki site
【Speaker】Dr. Ikutaro Hamada / 濱田幾太郎氏
【Affiliation】WPI-AIMR, Tohoku University / 東北大学 WPI-AIMR
【Title】Impact of adsorbates on water-surface interaction: A density functional theory study
【Abstract】
Interaction of water with a surface has been studied extensively, because it has implications for various fields ranging from daily life to science and technology, including wetting, lubrication, corrosion, heterogeneous catalysis, and electrochemistry. In many theoretical studies of water on metal surfaces, only clean surfaces were considered, and less attention has been paid for the interaction of water with adsorbates and that between adsorbates. However, these interactions are particularly important in electrochemistry, as they are directly related to heterogeneous catalytic reactions at electrode/electrolyte interfaces. In this talk, I will introduced density functional theory study of interactions between water and metal surfaces with and without adsorbate and discuss how the specific adsorbates modify the water-surface interactions. I will discuss the implication to the electrochemistry and how the surface science approach helps to understand the complex electrochemical interfaces.
【Contact】Dr. Yoshitaka Tateyama(館山佳尚)
Floquet Topological Quantum Phase Transitions in the transverse Wen-Plaquette Model
Mr. Victor Manuel Bastidas Valencia
【Date & Time】6 February 2013 (Wed.) 15:00-16:00
【Place】4F room 409/410, Collaborative Bldg., Namiki site
【Speaker】Mr. Victor Manuel Bastidas Valencia
【Affiliation】Institut fuer Theoretische Physik, Technische Universitaet Berlin
【Title】Floquet Topological Quantum Phase Transitions in the transverse Wen-Plaquette Model
【Abstract】
Symmetry breaking is a paradigm of condensed matter physics in which the states of matter are characterized as symmetry broken phases. However, rather recently, novel states of matter have been discovered, a topological quantum phase transition (TQPT), which cannot be classified inside the Landau criteria. Topological states of matter are characterized by an intrinsic robustness against the effects of an environment as a consequence of the topological properties of the ground state.
The current feasibilities of the experimental methods to control and simulate quantum many-body systems allow to experimentally explore the nonequilibrium dynamics of systems under the effect of an external driving. In particular, this opens the possibility to investigate spin systems with topological order in nonequilibrium, which have a huge potential for applications in quantum information technologies as topologically-protected qubits.
In this talk I will discuss the TQPT in a spin model termed Wen-plaquette model (WPM) in a time-dependent transverse field. In the absence of driving, the transverse WPM exhibits a TQPT from a spin-polarized phase to a topologically-ordered phase. I will discuss generalized "string"-like topological order parameters by considering cycle-averaged expectation values of string operators in a Floquet state.
【Contact】Dr. Junichi Inoue(井上純一)
【Place】4F room 409/410, Collaborative Bldg., Namiki site
【Speaker】Mr. Victor Manuel Bastidas Valencia
【Affiliation】Institut fuer Theoretische Physik, Technische Universitaet Berlin
【Title】Floquet Topological Quantum Phase Transitions in the transverse Wen-Plaquette Model
【Abstract】
Symmetry breaking is a paradigm of condensed matter physics in which the states of matter are characterized as symmetry broken phases. However, rather recently, novel states of matter have been discovered, a topological quantum phase transition (TQPT), which cannot be classified inside the Landau criteria. Topological states of matter are characterized by an intrinsic robustness against the effects of an environment as a consequence of the topological properties of the ground state.
The current feasibilities of the experimental methods to control and simulate quantum many-body systems allow to experimentally explore the nonequilibrium dynamics of systems under the effect of an external driving. In particular, this opens the possibility to investigate spin systems with topological order in nonequilibrium, which have a huge potential for applications in quantum information technologies as topologically-protected qubits.
In this talk I will discuss the TQPT in a spin model termed Wen-plaquette model (WPM) in a time-dependent transverse field. In the absence of driving, the transverse WPM exhibits a TQPT from a spin-polarized phase to a topologically-ordered phase. I will discuss generalized "string"-like topological order parameters by considering cycle-averaged expectation values of string operators in a Floquet state.
【Contact】Dr. Junichi Inoue(井上純一)
Recent advances in computational chemistry:from excited state dynamics to gold
Prof. Tetsuya Taketsugu / 武次徹也教授
【Date & Time】30 January 2013 (Wed), 16:00 - 17:00
【Place】Auditorium, 1F, WPI-MANA bldg. Namiki site
【Speaker】Prof. Tetsuya Taketsugu / 武次徹也教授
【Affiliation】Dept. of Chemistry, Faculty of Science, Hokkaido University/北海道大学 大学院理学研究院化学部門
【Title】Recent advances in computational chemistry:from excited state dynamics to gold nanocatalysts
【Abstract】
In this talk, I introduce our recent researches in the field of computational chemistry: (1) surface-hopping ab initio molecular dynamics (SH-AIMD) study and (2) theoretical study of gold nanocatalysts. In the first topic, I briefly explain theoretical methodology of the SH-AIMD method, and then discuss recent application to the photoisomerization of cis- and trans-azobenzene. The present SH-AIMD simulations at the SA-CASSCF level, as well as examination of the excited-state potential energy surfaces at the CASPT2 level, are shown to clarify the reaction pathways and dynamics of photo-excited azobenzene. In the second topic, I discuss electronic and geometric features of small gold clusters, and show some application of global reaction route mapping (GRRM) to gold clusters. The role of support effect in the catalytic activity of gold clusters is also discussed.
【Contact】Dr. Yoshitaka Tateyama(館山佳尚)
【Place】Auditorium, 1F, WPI-MANA bldg. Namiki site
【Speaker】Prof. Tetsuya Taketsugu / 武次徹也教授
【Affiliation】Dept. of Chemistry, Faculty of Science, Hokkaido University/北海道大学 大学院理学研究院化学部門
【Title】Recent advances in computational chemistry:from excited state dynamics to gold nanocatalysts
【Abstract】
In this talk, I introduce our recent researches in the field of computational chemistry: (1) surface-hopping ab initio molecular dynamics (SH-AIMD) study and (2) theoretical study of gold nanocatalysts. In the first topic, I briefly explain theoretical methodology of the SH-AIMD method, and then discuss recent application to the photoisomerization of cis- and trans-azobenzene. The present SH-AIMD simulations at the SA-CASSCF level, as well as examination of the excited-state potential energy surfaces at the CASPT2 level, are shown to clarify the reaction pathways and dynamics of photo-excited azobenzene. In the second topic, I discuss electronic and geometric features of small gold clusters, and show some application of global reaction route mapping (GRRM) to gold clusters. The role of support effect in the catalytic activity of gold clusters is also discussed.
【Contact】Dr. Yoshitaka Tateyama(館山佳尚)
DFT Modified Poisson-Boltzmann calculations on electrode reactions in fuel cells technology
Dr. Ryosuke Jinnouchi / 陣内亮典氏
【Date & Time】25 January 2013 (Fri), 16:15 - 17:00
【Place】Auditorium, 1F, WPI-MANA bldg. Namiki site
【Speaker】Dr. Ryosuke Jinnouchi / 陣内亮典氏
【Affiliation】Electrochemitry Div., Toyota Central R&D Labs., Inc./ 豊田中研
【Title】DFT Modified Poisson-Boltzmann calculations on electrode reactions in fuel cells technology
【Abstract】
This short talk presents a theory for electrified liquid-solid interfaces we have developed, which employs the density functional theory (DFT) and a modified Poisson-Boltzmann (MPB) theory for describing Helmholtz layers and diffusion layers in long-ranged electric double layers, respectively. After a brief description on the equations and models used in this theory, results are presented on applications to electro-oxidation of Pt surfaces, specific adsorption of sulfuric acid anion and underpotential deposition of Cu. Those results show that the theory can predict, with a useful accuracy, the reversible potentials of electron transfer reactions in both non-adsorbed and adsorbed phases.
【Contact】Dr. Yoshitaka Tateyama(館山佳尚)
【Place】Auditorium, 1F, WPI-MANA bldg. Namiki site
【Speaker】Dr. Ryosuke Jinnouchi / 陣内亮典氏
【Affiliation】Electrochemitry Div., Toyota Central R&D Labs., Inc./ 豊田中研
【Title】DFT Modified Poisson-Boltzmann calculations on electrode reactions in fuel cells technology
【Abstract】
This short talk presents a theory for electrified liquid-solid interfaces we have developed, which employs the density functional theory (DFT) and a modified Poisson-Boltzmann (MPB) theory for describing Helmholtz layers and diffusion layers in long-ranged electric double layers, respectively. After a brief description on the equations and models used in this theory, results are presented on applications to electro-oxidation of Pt surfaces, specific adsorption of sulfuric acid anion and underpotential deposition of Cu. Those results show that the theory can predict, with a useful accuracy, the reversible potentials of electron transfer reactions in both non-adsorbed and adsorbed phases.
【Contact】Dr. Yoshitaka Tateyama(館山佳尚)