CMSセミナー2009
フラグメント分子軌道法による分子動力学シミュレーション /
Fragment MO Molecular Dynamics (FMO-MD)
Dr. Yuto Komeiji(古明地勇人博士)
【Date & Time】17 November 2009 (Tue), 13:30 am - 15:00 am
【Place】6F seminar room, Central Bldg., Sengen site
【Speaker】Dr. Yuto Komeiji(古明地勇人博士)
【Affiliation】AIST & Rikkyo Univ. (産総研計算科学研究部門&立教大学大学院理学系研究科)
【Title】フラグメント分子軌道法による分子動力学シミュレーション /
Fragment MO Molecular Dynamics (FMO-MD)
【Abstract】
北浦らが1999年に発表したフラグメント分子軌道法(Fragment molecular orbital method, FMO)は、巨大分子系の電子状態計算法として、発展してきた。2003年には、FMO法を利用した分子動力学法、FMO-MD法も開発され、最近は、水溶液中の低分子化合物を対象に、応用計算がなされるようになってきた。今回のセミナーでは、以下の内容を中心に、FMO-MDの様々な側面を紹介したい。
・FMO法の原理と計算例（水溶液中のタンパク質の電子状態）
・FMO-MD法の原理とプログラム(PEACH/ABINIT-MPXシステム、ブルームーン法）
・FMO-MD法の応用計算（SN2反応のシミュレーション）
・FMO-MD法の改良（３体効果の導入と汎用自動分割アルゴリズム）
【Contact】Dr. Hiori Kino(木野日織）
【Place】6F seminar room, Central Bldg., Sengen site
【Speaker】Dr. Yuto Komeiji(古明地勇人博士)
【Affiliation】AIST & Rikkyo Univ. (産総研計算科学研究部門&立教大学大学院理学系研究科)
【Title】フラグメント分子軌道法による分子動力学シミュレーション /
Fragment MO Molecular Dynamics (FMO-MD)
【Abstract】
北浦らが1999年に発表したフラグメント分子軌道法(Fragment molecular orbital method, FMO)は、巨大分子系の電子状態計算法として、発展してきた。2003年には、FMO法を利用した分子動力学法、FMO-MD法も開発され、最近は、水溶液中の低分子化合物を対象に、応用計算がなされるようになってきた。今回のセミナーでは、以下の内容を中心に、FMO-MDの様々な側面を紹介したい。
・FMO法の原理と計算例（水溶液中のタンパク質の電子状態）
・FMO-MD法の原理とプログラム(PEACH/ABINIT-MPXシステム、ブルームーン法）
・FMO-MD法の応用計算（SN2反応のシミュレーション）
・FMO-MD法の改良（３体効果の導入と汎用自動分割アルゴリズム）
【Contact】Dr. Hiori Kino(木野日織）
Normal-State Spin Dynamics and Temperature-Dependent Spin Resonance Energy in an Optimally Doped Iron Arsenide Superconductor
Dr. Vladimir Hinkov
【Date & Time】7 September 2009 (Mon) 14:30 – 16:00
【Place】8F large seminar room, Sengen site
【Speaker】Dr. Vladimir Hinkov
【Affiliation】Max-Planck-Institute for Solid State Research
【Title】Normal-State Spin Dynamics and Temperature-Dependent Spin Resonance Energy in an Optimally Doped Iron Arsenide Superconductor
【Abstract】
Using inelastic neutron scattering we have studied the spin excitations in optimally doped BaFe(1.85)Co(0.15)As(2) (Tc = 25 K) over a wide range of temperatures and energies. I will contrast our results to findings in cuprates and heavy fermion superconductors, and discuss their implications to theory. In particular, we find that in contrast to cuprates, the spectrum is in good agreement with predictions of the theory of nearly antiferromagnetic metals, without complications arising from a pseudogap or competing incommensurate spin-modulated phases. This simplifies the theoretical treatment, and our data provide the foundation for the development of quantitative theories of magnetically mediated superconductivity in the iron arsenides.
【Contact】Dr. Hiroyuki Yamase(山瀬博之)
【Place】8F large seminar room, Sengen site
【Speaker】Dr. Vladimir Hinkov
【Affiliation】Max-Planck-Institute for Solid State Research
【Title】Normal-State Spin Dynamics and Temperature-Dependent Spin Resonance Energy in an Optimally Doped Iron Arsenide Superconductor
【Abstract】
Using inelastic neutron scattering we have studied the spin excitations in optimally doped BaFe(1.85)Co(0.15)As(2) (Tc = 25 K) over a wide range of temperatures and energies. I will contrast our results to findings in cuprates and heavy fermion superconductors, and discuss their implications to theory. In particular, we find that in contrast to cuprates, the spectrum is in good agreement with predictions of the theory of nearly antiferromagnetic metals, without complications arising from a pseudogap or competing incommensurate spin-modulated phases. This simplifies the theoretical treatment, and our data provide the foundation for the development of quantitative theories of magnetically mediated superconductivity in the iron arsenides.
【Contact】Dr. Hiroyuki Yamase(山瀬博之)
Molecular dynamics simulations of hysteresis loops for BaTiO3 ferroelectric thin-film capacitors using the feram code
Dr. Takeshi Nishimatsu(西松毅博士)
【Date & Time】4 September 2009 (Fri) 15:30 – 17:00
【Place】5F seminar room, Sengen site
【Speaker】Dr. Takeshi Nishimatsu(西松毅博士)
【Affiliation】Institute for Materials Research, Tohoku University (東北大学金属材料研究所)
【Title】Molecular dynamics simulations of hysteresis loops for BaTiO3 ferroelectric thin-film capacitors using the feram code
【Abstract】
Molecular dynamics (MD) simulations of hysteresis loops are performed for bulk and thin-film BaTiO3 using our original MD code, "feram" (http://loto.sf.net/feram/) [1]. "feram" can simulate temperature, thickness, frequency and electrode dependences of ferroelectric properties. We confirmed that the imperfect screening by the electrodes decreases the coercive field as the film thickness decreases in thin-film ferroelectric capacitors, as described in Ref. [2]. We also found that compressive strain arising from epitaxial constraints suppresses the polarization switching, while the inclusion of inhomogeneous strain (i.e. acoustic displacements) eases the switching.
[1] Takeshi Nishimatsu, Umesh V. Waghmare, Yoshiyuki Kawazoe, and David Vanderbilt: Phys. Rev. B 78 (2008) 104104.
[2] M. Dawber, P. Chandra, P. B. Littlewood and J. F. Scott: J. Phys.-Condes. Matter 15 (2003) L393.
【Contact】Dr. Taizo Sasaki(佐々木泰造)
【Place】5F seminar room, Sengen site
【Speaker】Dr. Takeshi Nishimatsu(西松毅博士)
【Affiliation】Institute for Materials Research, Tohoku University (東北大学金属材料研究所)
【Title】Molecular dynamics simulations of hysteresis loops for BaTiO3 ferroelectric thin-film capacitors using the feram code
【Abstract】
Molecular dynamics (MD) simulations of hysteresis loops are performed for bulk and thin-film BaTiO3 using our original MD code, "feram" (http://loto.sf.net/feram/) [1]. "feram" can simulate temperature, thickness, frequency and electrode dependences of ferroelectric properties. We confirmed that the imperfect screening by the electrodes decreases the coercive field as the film thickness decreases in thin-film ferroelectric capacitors, as described in Ref. [2]. We also found that compressive strain arising from epitaxial constraints suppresses the polarization switching, while the inclusion of inhomogeneous strain (i.e. acoustic displacements) eases the switching.
[1] Takeshi Nishimatsu, Umesh V. Waghmare, Yoshiyuki Kawazoe, and David Vanderbilt: Phys. Rev. B 78 (2008) 104104.
[2] M. Dawber, P. Chandra, P. B. Littlewood and J. F. Scott: J. Phys.-Condes. Matter 15 (2003) L393.
【Contact】Dr. Taizo Sasaki(佐々木泰造)
Linear scaling algorithms: introduction, accuracy, and scalable implementation
Dr. Vincent Sacksteder
【Date & Time】16 July 2009 (Thu) 10:30 – 12:00
【Place】8F large seminar room, Sengen site
【Speaker】Dr. Vincent Sacksteder
【Affiliation】Asia Pacific Center for Theoretical Physics, South Korea
【Title】Linear scaling algorithms: introduction, accuracy, and scalable implementation
【Abstract】
This talk introduces the main ideas of linear scaling algorithms, which promise to extend first principles DFT calculations to large numbers of atoms and large parallel supercomputers. Physically speaking they are implementations of the idea callednearsightedness. I argue that linear scaling algorithms can be exponentially accurate even in metals as long as there is some disorder. Lastly I discuss the enormous difference between having a scalable algorithm and having an implementation which scales to the largest supercomputers, and propose development of a general purpose library for linear scaling codes.
【Contact】Dr. Tsuyoshi Miyazaki(宮崎剛)
【Place】8F large seminar room, Sengen site
【Speaker】Dr. Vincent Sacksteder
【Affiliation】Asia Pacific Center for Theoretical Physics, South Korea
【Title】Linear scaling algorithms: introduction, accuracy, and scalable implementation
【Abstract】
This talk introduces the main ideas of linear scaling algorithms, which promise to extend first principles DFT calculations to large numbers of atoms and large parallel supercomputers. Physically speaking they are implementations of the idea callednearsightedness. I argue that linear scaling algorithms can be exponentially accurate even in metals as long as there is some disorder. Lastly I discuss the enormous difference between having a scalable algorithm and having an implementation which scales to the largest supercomputers, and propose development of a general purpose library for linear scaling codes.
【Contact】Dr. Tsuyoshi Miyazaki(宮崎剛)
Theory of quantum transport in superconductor/ferromagnet hybrid junctions
超伝導/強磁性接合における量子輸送現象の理論
Dr. Shin-ichi Hikino (挽野真一博士)
【Date & Time】13 July 2009 (Mon) 15:30 – 17:00
【Place】8F large seminar room, Sengen site
【Speaker】Dr. Shin-ichi Hikino (挽野真一博士)
【Affiliation】Institute for Materials Research, Tohoku University (東北大学金属材料研究所)
【Title】Theory of quantum transport in superconductor/ferromagnet hybrid junctions
超伝導/強磁性接合における量子輸送現象の理論
【Abstract】
In a Josephson junction with a ferromagnet (FM), which is called the ferromagnetic Josephson junction (FJJ), the Cooper pairs penetrate into the FM and have additional momenta due to the exchange energy in the FM. As a result, the phase of the superconducting order parameter shifts by π. The so-called π-state has been studied extensively. However, the magnetic scattering and magnetization dynamics for Cooper pair has not received much attention in the study of FJJs. Moreover, most of studies on the FJJs have been so far focused on the dc Josephson effect. In this talk, I present three topics: (1) Effect of magnetic scattering in a ferromagnetic Josephson junction, (2) AC Josephson current in a ferromagnetic Josephson junction, and (3) Theory of ferromagnetic Josephson resonance.
【Contact】Dr. Hiroyuki Yamase(山瀬博之)
【Place】8F large seminar room, Sengen site
【Speaker】Dr. Shin-ichi Hikino (挽野真一博士)
【Affiliation】Institute for Materials Research, Tohoku University (東北大学金属材料研究所)
【Title】Theory of quantum transport in superconductor/ferromagnet hybrid junctions
超伝導/強磁性接合における量子輸送現象の理論
【Abstract】
In a Josephson junction with a ferromagnet (FM), which is called the ferromagnetic Josephson junction (FJJ), the Cooper pairs penetrate into the FM and have additional momenta due to the exchange energy in the FM. As a result, the phase of the superconducting order parameter shifts by π. The so-called π-state has been studied extensively. However, the magnetic scattering and magnetization dynamics for Cooper pair has not received much attention in the study of FJJs. Moreover, most of studies on the FJJs have been so far focused on the dc Josephson effect. In this talk, I present three topics: (1) Effect of magnetic scattering in a ferromagnetic Josephson junction, (2) AC Josephson current in a ferromagnetic Josephson junction, and (3) Theory of ferromagnetic Josephson resonance.
【Contact】Dr. Hiroyuki Yamase(山瀬博之)
Quantum Network Model and its Application to Quantum Transport Phenomenna
Prof. Tomi Ohtsuki (大槻東巳教授)
【Date & Time】8 July 2009 (Wed), 15:30-17:00
【Place】4F seminar room, MANA building, Namiki Site
【Speaker】Prof. Tomi Ohtsuki (大槻東巳教授)
【Affiliation】Sophia University (上智大学理工学部)
【Title】Quantum Network Model and its Application to Quantum Transport Phenomenna
【Abstract】
Quantum network models, which were originally introduced by Chalker and Coddington to explain the quantum Hall effect, have proved capable of describing a wide range of transport phenomena in disordered systems. Here I give a talk on a series of studies for quantum transport phenomena such as the quantum Hall effect and quantum spin Hall effect, and the effect of perfectly conducting channel.
【Contact】Dr. Katsunori Wakabayashi(若林克法)
【Place】4F seminar room, MANA building, Namiki Site
【Speaker】Prof. Tomi Ohtsuki (大槻東巳教授)
【Affiliation】Sophia University (上智大学理工学部)
【Title】Quantum Network Model and its Application to Quantum Transport Phenomenna
【Abstract】
Quantum network models, which were originally introduced by Chalker and Coddington to explain the quantum Hall effect, have proved capable of describing a wide range of transport phenomena in disordered systems. Here I give a talk on a series of studies for quantum transport phenomena such as the quantum Hall effect and quantum spin Hall effect, and the effect of perfectly conducting channel.
【Contact】Dr. Katsunori Wakabayashi(若林克法)
Recent developments in non-centrosymmetric superconductors
Prof. Manfred Sigrist
【Date & Time】6 July 2009 (Mon), 10:30 – 12:00
【Place】8F large seminar room, Sengen site
【Speaker】Prof. Manfred Sigrist
【Affiliation】Theoretische Physik, ETH Zurich(スイス連邦工科大学チューリッヒ校理論物理学研究所)
【Title】Recent developments in non-centrosymmetric superconductors
【Abstract】
The absence of inversion symmetry in a metal influences the electronic spectrum drastically through spin-orbit coupling by spin-splitting of the states. This affects superconductivity in a special way through a novel Cooper pairing symmetry which is non-unitary and has mixed-parity nature. The study of this type of superconductivity has been mainly motivated by the recent discovery of a number of noncentrosymmetric heavy fermion superconductors, such as CePt3 Si, CeRhSi3 or CeIrSi3 . In this talk I will present the basic concepts of non-centrosymmetric superconductivity and explore some experimental implications for the superconducting phase. In particular, properties in high magnetic fields, the electronic states at twin boundaries and surfaces will be discussed.
【Contact】Dr. Katsunori Wakabayashi(若林克法)
【Place】8F large seminar room, Sengen site
【Speaker】Prof. Manfred Sigrist
【Affiliation】Theoretische Physik, ETH Zurich(スイス連邦工科大学チューリッヒ校理論物理学研究所)
【Title】Recent developments in non-centrosymmetric superconductors
【Abstract】
The absence of inversion symmetry in a metal influences the electronic spectrum drastically through spin-orbit coupling by spin-splitting of the states. This affects superconductivity in a special way through a novel Cooper pairing symmetry which is non-unitary and has mixed-parity nature. The study of this type of superconductivity has been mainly motivated by the recent discovery of a number of noncentrosymmetric heavy fermion superconductors, such as CePt3 Si, CeRhSi3 or CeIrSi3 . In this talk I will present the basic concepts of non-centrosymmetric superconductivity and explore some experimental implications for the superconducting phase. In particular, properties in high magnetic fields, the electronic states at twin boundaries and surfaces will be discussed.
【Contact】Dr. Katsunori Wakabayashi(若林克法)
Recent Developments in Conquest:Million Atom DFT and Constrained DFT
Dr. David Bowler
【Date & Time】29 June (Mon) 15:30 - 17:00
【Place】8F large seminar room (８階中セミナー室), SENGEN site
【Speaker】Dr. David Bowler
【Affiliation】Department of Physics & Astronomy, University College London (UCL)
【Title】Recent Developments in Conquest:Million Atom DFT and Constrained DFT
【Abstract】
I will give a description of the linear scaling DFT code Conquest, which has been developed at UCL and NIMS. In particular, I will present recent results on the scaling of the code, and show that it scales perfectly to over 4,000 cores and 2,000,000 atoms on modern high-performance computers. This demonstrates the potential of DFT to address systems of millions of atoms.
I will also discuss the implementation of constrained DFT within the code, and give details of how this method can be used to calculate charge transfer and excitation properties of systems using DFT. I will discuss plans for the application and development of Conquest.
【Contact】Dr. Yoshitaka Tateyama(館山佳尚)
【Place】8F large seminar room (８階中セミナー室), SENGEN site
【Speaker】Dr. David Bowler
【Affiliation】Department of Physics & Astronomy, University College London (UCL)
【Title】Recent Developments in Conquest:Million Atom DFT and Constrained DFT
【Abstract】
I will give a description of the linear scaling DFT code Conquest, which has been developed at UCL and NIMS. In particular, I will present recent results on the scaling of the code, and show that it scales perfectly to over 4,000 cores and 2,000,000 atoms on modern high-performance computers. This demonstrates the potential of DFT to address systems of millions of atoms.
I will also discuss the implementation of constrained DFT within the code, and give details of how this method can be used to calculate charge transfer and excitation properties of systems using DFT. I will discuss plans for the application and development of Conquest.
【Contact】Dr. Yoshitaka Tateyama(館山佳尚)
Electronic Transport of Nanographene: Effect of Geometry and Edges
Dr. Katsunori Wakabayashi (若林 克法 博士)
【Date & Time】10 June 2009 (Wed) 3:30 pm - 5:00 pm
【Place】8F large seminar room, SENGEN site
【Speaker】Dr. Katsunori Wakabayashi (若林 克法 博士)
【Affiliation】NIMS-MANA & JST-PRESTO(NIMS国際ナノアーキテクトニクス研究拠点・JSTさきがけ)
【Title】Electronic Transport of Nanographene: Effect of Geometry and Edges
【Abstract】
The successive fabrication of graphene devices has has initiated intensive and diverse research on carbon related systems. The honeycomb crystal structure of single layer graphene consists of two nonequivalent sublattices and results in a unique band structure for the itinerant p-electrons near the Fermi energy which behave as massless Dirac fermion. In graphene, the presence of edges can have strong implications for the spectrum of the p-electrons. In graphene nanoribbons with zigzag edges, localized states appear at the edge with energies close to the Fermi level. In contrast, edge states are absent for ribbons with armchair edges. Recent experiments have succeeded to synthesize graphene nanoribbons using lithography techniques and chemical techniques. In my talk, we focus on edge and geometry effects of the electronic transport properties of graphene nanoribbons. (1) In zigzag nanoribbons, for disorder without inter-valley scattering a single perfectly conducting channel emerges associated with such a chiral mode due to edge states, i.e. the absence of the localization. (2) In armchair nanoribbons, the single-channel transport subjected to long-ranged impurities is nearly perfectly conducting, where the backward scattering matrix elements in the lowest order vanish as a manifestation of internal phase structures of the wavefunction. (3) Nano-graphene junctions are shown to have the zero-conductance anti-resoances associated with the edge states. The relation between the condition of the resonances and geometry is discussed.
【Contact】Dr. Yoshitaka Tateyama(館山佳尚)
【Place】8F large seminar room, SENGEN site
【Speaker】Dr. Katsunori Wakabayashi (若林 克法 博士)
【Affiliation】NIMS-MANA & JST-PRESTO(NIMS国際ナノアーキテクトニクス研究拠点・JSTさきがけ)
【Title】Electronic Transport of Nanographene: Effect of Geometry and Edges
【Abstract】
The successive fabrication of graphene devices has has initiated intensive and diverse research on carbon related systems. The honeycomb crystal structure of single layer graphene consists of two nonequivalent sublattices and results in a unique band structure for the itinerant p-electrons near the Fermi energy which behave as massless Dirac fermion. In graphene, the presence of edges can have strong implications for the spectrum of the p-electrons. In graphene nanoribbons with zigzag edges, localized states appear at the edge with energies close to the Fermi level. In contrast, edge states are absent for ribbons with armchair edges. Recent experiments have succeeded to synthesize graphene nanoribbons using lithography techniques and chemical techniques. In my talk, we focus on edge and geometry effects of the electronic transport properties of graphene nanoribbons. (1) In zigzag nanoribbons, for disorder without inter-valley scattering a single perfectly conducting channel emerges associated with such a chiral mode due to edge states, i.e. the absence of the localization. (2) In armchair nanoribbons, the single-channel transport subjected to long-ranged impurities is nearly perfectly conducting, where the backward scattering matrix elements in the lowest order vanish as a manifestation of internal phase structures of the wavefunction. (3) Nano-graphene junctions are shown to have the zero-conductance anti-resoances associated with the edge states. The relation between the condition of the resonances and geometry is discussed.
【Contact】Dr. Yoshitaka Tateyama(館山佳尚)
Symmetry breaking in superconductors and superfluid : Spin triplet superconductivity in Sr2RuO4
超伝導・超流動における対称性の破れ：Sr2RuO4 のスピン三重項超伝導
Dr. Youichi Yanase (柳瀬陽一博士)
【Date & Time】20 May 2009 (Wed), 3:30 pm - 5:00 pm
【Place】8F large seminar room, Sengen site
【Speaker】Dr. Youichi Yanase (柳瀬陽一博士)
【Affiliation】Department of Physics, University of Tokyo (東京大学大学院理学研究科物理学専攻)
【Title】Symmetry breaking in superconductors and superfluid : Spin triplet superconductivity in Sr2RuO4
超伝導・超流動における対称性の破れ：Sr2RuO4 のスピン三重項超伝導
【Abstract】
Superconductors and superfluid which have multi-component order parameters are the playground of the novel quantum condenced phase leading to the spontaneous symmetry breaking. I will introduce the basic concept of the symmetry breaking in the superconductor/superfluid and talk about the recent developments in this research field. In particular, the spin triplet superconductivity in Sr2RuO4 is discussed in details as a typical example.
【Contact】Dr. Hiroyuki Yamase(山瀬博之)
【Place】8F large seminar room, Sengen site
【Speaker】Dr. Youichi Yanase (柳瀬陽一博士)
【Affiliation】Department of Physics, University of Tokyo (東京大学大学院理学研究科物理学専攻)
【Title】Symmetry breaking in superconductors and superfluid : Spin triplet superconductivity in Sr2RuO4
超伝導・超流動における対称性の破れ：Sr2RuO4 のスピン三重項超伝導
【Abstract】
Superconductors and superfluid which have multi-component order parameters are the playground of the novel quantum condenced phase leading to the spontaneous symmetry breaking. I will introduce the basic concept of the symmetry breaking in the superconductor/superfluid and talk about the recent developments in this research field. In particular, the spin triplet superconductivity in Sr2RuO4 is discussed in details as a typical example.
【Contact】Dr. Hiroyuki Yamase(山瀬博之)
Finding the global minimum among zillions of local minima : Methods for global geometry optimization of molecular structures
Prof. Stefan Goedecker
【Date & Time】9 April (Thu), 3:30 pm - 5:00 pm
【Place】4F seminar room, Collaborative Res. Bldg.（共同研究棟）, Namiki site
【Speaker】Prof. Stefan Goedecker
【Affiliation】Department of Physics and Astronomy, University of Basel
【Title】Finding the global minimum among zillions of local minima : Methods for global geometry optimization of molecular structures
【Abstract】
The number of local minima grows exponentially with respect to the number of atoms in a molecule or cluster. Finding the global minimum becomes therefore an extremely difficult task for large systems. I will introduce the Minima Hopping method and explain the ingredients which make it efficient. In particular I will discuss the importance of the Bell-Evan-Polyani principle for global optimization. I will also contrast the minima hopping method with two other widely used global optimization methods, namely genetic algorithms and basin hopping.
【Contact】Dr. Yoshitaka Tateyama(館山佳尚)
【Place】4F seminar room, Collaborative Res. Bldg.（共同研究棟）, Namiki site
【Speaker】Prof. Stefan Goedecker
【Affiliation】Department of Physics and Astronomy, University of Basel
【Title】Finding the global minimum among zillions of local minima : Methods for global geometry optimization of molecular structures
【Abstract】
The number of local minima grows exponentially with respect to the number of atoms in a molecule or cluster. Finding the global minimum becomes therefore an extremely difficult task for large systems. I will introduce the Minima Hopping method and explain the ingredients which make it efficient. In particular I will discuss the importance of the Bell-Evan-Polyani principle for global optimization. I will also contrast the minima hopping method with two other widely used global optimization methods, namely genetic algorithms and basin hopping.
【Contact】Dr. Yoshitaka Tateyama(館山佳尚)
Free energy calculation for chemical reactions in condensed systems by the QM/MM approach combined with a theory of solutions
Prof. Hideaki Takahashi (高橋英明准教授)
【Date & Time】18 March 2009 (Wed), 3:30 pm - 5:00 pm
【Place】8F large seminar room, Sengen site
【Speaker】Prof. Hideaki Takahashi (高橋英明准教授)
【Affiliation】Graduate School of Engineering Science, Osaka University (大阪大学大学院基礎工学研究科)
【Title】Free energy calculation for chemical reactions in condensed systems by the QM/MM approach combined with a theory of solutions
【Abstract】
The quantity that governs the reaction pathway in a condensed system is, of course, the free energy change associated with the chemical process. Hence, it is of primary importance to develop an efficient method to compute free energy change for chemical events in many- particle systems. There are, however, two major difficulties in computing the free energy. One is related to the quantum chemical calculations for large systems and another is to the free energy calculation by the method of molecular simulations. Our strategy to overcome these obstacles is to combine the QM/MM approach and a novel theory of solutions termed as the theory of energy representation. Our recent works demonstrated that the approach is efficient and accurate for the computation of the free energies. In this seminar we give the outline of the method and present some applications to chemical reactions in solutions and biological systems.
【Contact】Dr. Tsuyoshi Miyazaki(宮崎剛)
【Place】8F large seminar room, Sengen site
【Speaker】Prof. Hideaki Takahashi (高橋英明准教授)
【Affiliation】Graduate School of Engineering Science, Osaka University (大阪大学大学院基礎工学研究科)
【Title】Free energy calculation for chemical reactions in condensed systems by the QM/MM approach combined with a theory of solutions
【Abstract】
The quantity that governs the reaction pathway in a condensed system is, of course, the free energy change associated with the chemical process. Hence, it is of primary importance to develop an efficient method to compute free energy change for chemical events in many- particle systems. There are, however, two major difficulties in computing the free energy. One is related to the quantum chemical calculations for large systems and another is to the free energy calculation by the method of molecular simulations. Our strategy to overcome these obstacles is to combine the QM/MM approach and a novel theory of solutions termed as the theory of energy representation. Our recent works demonstrated that the approach is efficient and accurate for the computation of the free energies. In this seminar we give the outline of the method and present some applications to chemical reactions in solutions and biological systems.
【Contact】Dr. Tsuyoshi Miyazaki(宮崎剛)
DFT challenges in catalysis and electrochemistry
Prof. Nicola Marzari
【Date & Time】23 February 2009 (Mon), 3:30 pm - 5:00 pm
【Place】4F seminar room, MANA Bldg., Namiki Site
【Speaker】Prof. Nicola Marzari
【Affiliation】Department of Materials Science and Engineering, Massachusetts Institute of Technology (MIT), USA
【Title】DFT challenges in catalysis and electrochemistry
【Abstract】
Quantum-mechanical simulations based on density-functional theory have become an extremely powerful tool to understand, predict, and design the properties of complex materials or devices. Simulations of many catalytic and electrochemical processes provide nevertheless significant challenges that directly affect our ability to develop new materials for energy storage and conversion from first-principles.
Notwithstanding these successes, there are key qualitative failures that affect the accuracy of calculations based on local or even hybrid exchange-correlation functionals, all rooted in spurious self-interaction errors. I will discuss some of these key challenges, and our suggested solutions, with examples drawn from the study of electron-transfer processes (ferrous-ferric exchange in water) and catalytic reactions at transition-metal complexes (addition-elimination of hydrogen at an iron center).
Last, I will discuss our approach to perform quantum simulations under applied electrochemical potentials (of relevance to fuel-cell reactions) and its application to the study of electrochemical Stark tuning in adsorbates.
【Contact】Dr. Yoshitaka Tateyama(館山佳尚)
【Place】4F seminar room, MANA Bldg., Namiki Site
【Speaker】Prof. Nicola Marzari
【Affiliation】Department of Materials Science and Engineering, Massachusetts Institute of Technology (MIT), USA
【Title】DFT challenges in catalysis and electrochemistry
【Abstract】
Quantum-mechanical simulations based on density-functional theory have become an extremely powerful tool to understand, predict, and design the properties of complex materials or devices. Simulations of many catalytic and electrochemical processes provide nevertheless significant challenges that directly affect our ability to develop new materials for energy storage and conversion from first-principles.
Notwithstanding these successes, there are key qualitative failures that affect the accuracy of calculations based on local or even hybrid exchange-correlation functionals, all rooted in spurious self-interaction errors. I will discuss some of these key challenges, and our suggested solutions, with examples drawn from the study of electron-transfer processes (ferrous-ferric exchange in water) and catalytic reactions at transition-metal complexes (addition-elimination of hydrogen at an iron center).
Last, I will discuss our approach to perform quantum simulations under applied electrochemical potentials (of relevance to fuel-cell reactions) and its application to the study of electrochemical Stark tuning in adsorbates.
【Contact】Dr. Yoshitaka Tateyama(館山佳尚)
Re-examination of half-metallic ferromagnetism for doped LaMnO3 in quasiparticle self-consistent GW method
Prof. Takao Kotani (小谷岳生教授)
【Date & Time】12 February 2009 (Thur), 10:00 am - 11:30 am
【Place】6F seminar room, Central Bldg., Sengen site
【Speaker】Prof. Takao Kotani (小谷岳生教授)
【Affiliation】Department of Applied Mathematics and Physics, Tottori University (鳥取大学大学院工学研究科)
【Title】Re-examination of half-metallic ferromagnetism for doped LaMnO3 in quasiparticle self-consistent GW method
【Abstract】
In this talk, we first describe the quasiparticle self-consistent GW (QSGW ) method, which can treat wide range of materials very well. Especially, we applied it to MnO and NiO, and have recently calculated their spin wave dispersions based on the QSGW [1]. They are in good agreement with experiments. Then we now apply it to a cubic virtual-crystal alloy La1-xBaxMnO3 (LBMO) as a theoretical representative for colossal magnetoresistive perovskite manganites. The QSGW predicts LBMO as a fully-polarized half-metallic ferromagnet for a wide range of x and lattice constant. Calculated density of states and dielectric functions are consistent with experiments. In contrast, the energies of calculated spin wave (SW) are very low in comparison with experiments. This is affected neither by rhombohedral deformation nor the intrinsic deficiency in the QSGW method. Thus it will be necessary to include effects due to phonons, which is not included in our calculation, so as to reproduce the experimental SW energies.
[1] T. Kotani and M. van Schilfgaarde,J. Phys.: Condens. Matter 20, 295214 (2008).
[2] T. Kotani and H.Kino,arXiv:0812.4294.
【Contact】Dr. Hiori Kino(木野日織）
【Place】6F seminar room, Central Bldg., Sengen site
【Speaker】Prof. Takao Kotani (小谷岳生教授)
【Affiliation】Department of Applied Mathematics and Physics, Tottori University (鳥取大学大学院工学研究科)
【Title】Re-examination of half-metallic ferromagnetism for doped LaMnO3 in quasiparticle self-consistent GW method
【Abstract】
In this talk, we first describe the quasiparticle self-consistent GW (QSGW ) method, which can treat wide range of materials very well. Especially, we applied it to MnO and NiO, and have recently calculated their spin wave dispersions based on the QSGW [1]. They are in good agreement with experiments. Then we now apply it to a cubic virtual-crystal alloy La1-xBaxMnO3 (LBMO) as a theoretical representative for colossal magnetoresistive perovskite manganites. The QSGW predicts LBMO as a fully-polarized half-metallic ferromagnet for a wide range of x and lattice constant. Calculated density of states and dielectric functions are consistent with experiments. In contrast, the energies of calculated spin wave (SW) are very low in comparison with experiments. This is affected neither by rhombohedral deformation nor the intrinsic deficiency in the QSGW method. Thus it will be necessary to include effects due to phonons, which is not included in our calculation, so as to reproduce the experimental SW energies.
[1] T. Kotani and M. van Schilfgaarde,J. Phys.: Condens. Matter 20, 295214 (2008).
[2] T. Kotani and H.Kino,arXiv:0812.4294.
【Contact】Dr. Hiori Kino(木野日織）