CMSセミナー2007
Electronic structure of antiferromagnetic NiO in LDA+DMFT
LDA+DMFT法による反強磁性NiOの電子構造
Dr. Oki Miura(三浦沖博士)
【Date & Time】14 November 2007 (Wed), 3:30 pm - 5:00 pm
【Place】8F larger seminar room, Sengen site
【Speaker】Dr. Oki Miura(三浦沖博士)
【Affiliation】Fujiwara project, JST-CREST(JST-CREST 藤原プロジェクト)
【Title】Electronic structure of antiferromagnetic NiO in LDA+DMFT
LDA+DMFT法による反強磁性NiOの電子構造
【Abstract】
DMFT is based on mapping of many electron systems in bulk onto single impurity problem, where the on-site dynamical interaction is included and the inter-atomic interaction is neglected. The combination of LDA with DMFT, namely LDA+DMFT has been developed and applied to strongly correlated electron systems. In this talk we will show the application of the LDA+DMFT to antiferromagnetic NiO. The on-site Coulomb interaction enhances the hybridization between Ni-3d and O-2p bands and this causes the charge-transfer electronic structure and 4.3eV band gap. These effects obtained by the LDA+DMFT have good agreement with experimental XPS result.
DMFT（動的平均場理論）はサイト内の動的な電子相関を取り扱う手法である。近年、DMFTとLDAとの複合手法（LDA+DMFT法）の開発、及び強相関物質への適用が盛んに行われている。我々はこれまで、広範な強相関物質に適用可能なLDA+DMFT法の開発を進めてきた。本講演では、我々のLDA+DMFT法の概略、及び反強磁性NiOへの適用結果について述べる。得られた状態密度はXPSの実験と良く一致し、バンドギャップ4.3eV、電荷移動型電子構造がよく再現されている。これらの描像は、Niサイト内の動的な電子相関がNi-3dバンドとO-2pバンドとの強い混成を引き起こしたことに起因している。
【Contact】Dr. Masao Arai (新井正男)
【Place】8F larger seminar room, Sengen site
【Speaker】Dr. Oki Miura(三浦沖博士)
【Affiliation】Fujiwara project, JST-CREST(JST-CREST 藤原プロジェクト)
【Title】Electronic structure of antiferromagnetic NiO in LDA+DMFT
LDA+DMFT法による反強磁性NiOの電子構造
【Abstract】
DMFT is based on mapping of many electron systems in bulk onto single impurity problem, where the on-site dynamical interaction is included and the inter-atomic interaction is neglected. The combination of LDA with DMFT, namely LDA+DMFT has been developed and applied to strongly correlated electron systems. In this talk we will show the application of the LDA+DMFT to antiferromagnetic NiO. The on-site Coulomb interaction enhances the hybridization between Ni-3d and O-2p bands and this causes the charge-transfer electronic structure and 4.3eV band gap. These effects obtained by the LDA+DMFT have good agreement with experimental XPS result.
DMFT（動的平均場理論）はサイト内の動的な電子相関を取り扱う手法である。近年、DMFTとLDAとの複合手法（LDA+DMFT法）の開発、及び強相関物質への適用が盛んに行われている。我々はこれまで、広範な強相関物質に適用可能なLDA+DMFT法の開発を進めてきた。本講演では、我々のLDA+DMFT法の概略、及び反強磁性NiOへの適用結果について述べる。得られた状態密度はXPSの実験と良く一致し、バンドギャップ4.3eV、電荷移動型電子構造がよく再現されている。これらの描像は、Niサイト内の動的な電子相関がNi-3dバンドとO-2pバンドとの強い混成を引き起こしたことに起因している。
【Contact】Dr. Masao Arai (新井正男)
Recent progress on time-dependent density functional theory within linear response
TDDFT線形応答理論に関する最近の進展
Dr. Chunping Hu(胡春平博士)
【Date & Time】24 October 2007 (Wed), 4:00 pm - 5:30 pm
【Place】8F larger seminar room, Sengen site
【Speaker】Dr. Chunping Hu(胡春平博士)
【Affiliation】Institute for Solid State Physics, The University of Tokyo / JST-CREST( 東京大学物性研究所杉野研究室 / JST-CREST 博士研究員)
【Title】Recent progress on time-dependent density functional theory within linear response
TDDFT線形応答理論に関する最近の進展
【Abstract】
Time-dependent density functional theory (TDDFT) has gained enormous popularity in studying electronic excited states. In this seminar our recent research on TDDFT linear response theory will be presented. First we present modified linear response theory to improve TDDFT performance on Rydberg and charge-transfer excitation energies, which are systematically underestimated by conventional TDDFT. Second we present an efficient TDDFT method to calculate nonadiabatic couplings between the ground and excited states, and show that modified linear response theory can be applied to improve the accuracy near potential crossings.
時間依存密度汎関数法(TDDFT)は電子励起状態計算に優れた能力を発揮することで広く注目されている。講演ではTDDFT線形応答理論に関する我々の最近の研究成果について紹介する。第1は、TDDFTがRydberg励起や電荷移動励起の励起エネルギーを系統的に過少評価するという問題に対して、拡張線形応答理論という計算手法を提案することにより大幅に改善できることである。第2は我々が非断熱遷移過程に重要である非断熱結合係数をTDDFTで効率的に計算する手法を開発し、拡張線形応答理論の適用により交差点付近でも良好な計算結果が得られることである
【Contact】Dr. Yoshitaka Tateyama(館山佳尚)
【Place】8F larger seminar room, Sengen site
【Speaker】Dr. Chunping Hu(胡春平博士)
【Affiliation】Institute for Solid State Physics, The University of Tokyo / JST-CREST( 東京大学物性研究所杉野研究室 / JST-CREST 博士研究員)
【Title】Recent progress on time-dependent density functional theory within linear response
TDDFT線形応答理論に関する最近の進展
【Abstract】
Time-dependent density functional theory (TDDFT) has gained enormous popularity in studying electronic excited states. In this seminar our recent research on TDDFT linear response theory will be presented. First we present modified linear response theory to improve TDDFT performance on Rydberg and charge-transfer excitation energies, which are systematically underestimated by conventional TDDFT. Second we present an efficient TDDFT method to calculate nonadiabatic couplings between the ground and excited states, and show that modified linear response theory can be applied to improve the accuracy near potential crossings.
時間依存密度汎関数法(TDDFT)は電子励起状態計算に優れた能力を発揮することで広く注目されている。講演ではTDDFT線形応答理論に関する我々の最近の研究成果について紹介する。第1は、TDDFTがRydberg励起や電荷移動励起の励起エネルギーを系統的に過少評価するという問題に対して、拡張線形応答理論という計算手法を提案することにより大幅に改善できることである。第2は我々が非断熱遷移過程に重要である非断熱結合係数をTDDFTで効率的に計算する手法を開発し、拡張線形応答理論の適用により交差点付近でも良好な計算結果が得られることである
【Contact】Dr. Yoshitaka Tateyama(館山佳尚)
Physics of Vortex State in Type II Superconductor: From Basics to Applications
超伝導磁束量子状態の物理：基礎と応用
Dr. Xiao Hu(胡暁ディレクター)
【Date & Time】10 October 2007 (Wed), 3:30 pm - 5:00 pm
【Place】8F larger seminar room, Sengen site
【Speaker】Dr. Xiao Hu(胡暁ディレクター)
【Affiliation】Group Leader of Strong-Coupling Modeling group, NIMS-CMSC(NIMS-CMSC 強相関モデリングG グループリーダー)
【Title】Physics of Vortex State in Type II Superconductor: From Basics to Applications
超伝導磁束量子状態の物理：基礎と応用
【Abstract】
Magnetic field penetrates into type II superconductors as tiny, quantized fluxes associated with supercurrent vortices. Because of the repulsive force, these vortices form a regular pattern, known as the Abrikosov vortex lattice. Dr. Abrikosov got the 2003 Noble Prize for Physics because of this work back to 1957. Physics of vortex states has experienced significant developments since the discovery of high temperature superconductivity in cuprates in 1986. Those who want to know either the basics, or new topics and advanced applications of superconductivity vortex are welcome to the seminar.
第2種超伝導体に臨界磁場以上の磁場をかけると、量子化された小さな磁束線がバルクを貫き、磁束間の斥力により磁束格子が形成される。今からちょうど50年前に提案された第2種超伝導の研究は、20年前の銅酸化物高温超伝導の発見をきっかけに飛躍的な発展を遂げた。そして、2003年Abrikosov博士のノーベル物理学賞受賞。本講演では我々の研究結果の紹介を交えながら超伝導磁束量子状態の基礎と応用を概観したい。
【Contact】Dr. Yoshitaka Tateyama(館山佳尚)
【Place】8F larger seminar room, Sengen site
【Speaker】Dr. Xiao Hu(胡暁ディレクター)
【Affiliation】Group Leader of Strong-Coupling Modeling group, NIMS-CMSC(NIMS-CMSC 強相関モデリングG グループリーダー)
【Title】Physics of Vortex State in Type II Superconductor: From Basics to Applications
超伝導磁束量子状態の物理：基礎と応用
【Abstract】
Magnetic field penetrates into type II superconductors as tiny, quantized fluxes associated with supercurrent vortices. Because of the repulsive force, these vortices form a regular pattern, known as the Abrikosov vortex lattice. Dr. Abrikosov got the 2003 Noble Prize for Physics because of this work back to 1957. Physics of vortex states has experienced significant developments since the discovery of high temperature superconductivity in cuprates in 1986. Those who want to know either the basics, or new topics and advanced applications of superconductivity vortex are welcome to the seminar.
第2種超伝導体に臨界磁場以上の磁場をかけると、量子化された小さな磁束線がバルクを貫き、磁束間の斥力により磁束格子が形成される。今からちょうど50年前に提案された第2種超伝導の研究は、20年前の銅酸化物高温超伝導の発見をきっかけに飛躍的な発展を遂げた。そして、2003年Abrikosov博士のノーベル物理学賞受賞。本講演では我々の研究結果の紹介を交えながら超伝導磁束量子状態の基礎と応用を概観したい。
【Contact】Dr. Yoshitaka Tateyama(館山佳尚)
Density functional theory
Prof. Koichi Kusakabe(草部浩一准教授)
【Date & Time】2 October 2007 (Tue), 3:30 pm - 5:00 pm
【Place】8F larger seminar room, Sengen site
【Speaker】Prof. Koichi Kusakabe(草部浩一准教授)
【Affiliation】Graduate School of Engineering Science, Osaka University(大阪大学大学院基礎工学研究科)
【Title】Density functional theory / 密度汎関数法
【Abstract】
The density functional theory is a theory of the phase transition. The universal density functional given by Levy and Lieb is the first example of a Landau free energy exactly defined at the zero temperature. The single-particle density is the first order parameter in this theory. In this talk, I will show that the multi-reference extension of the Kohn-Sham scheme gives a way to have a self-consistent description of electronic states with multiple order parameters.
密度汎関数法は相転移の理論である。LevyとLiebが与えたユニバーサルエネルギー汎関数は絶対零度において厳密に定義されたランダウ・自由エネルギーである。一粒子密度はこの理論の第一秩序変数を与える。この講演では、コーン・シャム法の多配置参照型拡張が、複数の秩序変数をもつ電子状態の記述を与えることを示す。
【Contact】Dr. Yoshitaka Tateyama(館山佳尚)
【Place】8F larger seminar room, Sengen site
【Speaker】Prof. Koichi Kusakabe(草部浩一准教授)
【Affiliation】Graduate School of Engineering Science, Osaka University(大阪大学大学院基礎工学研究科)
【Title】Density functional theory / 密度汎関数法
【Abstract】
The density functional theory is a theory of the phase transition. The universal density functional given by Levy and Lieb is the first example of a Landau free energy exactly defined at the zero temperature. The single-particle density is the first order parameter in this theory. In this talk, I will show that the multi-reference extension of the Kohn-Sham scheme gives a way to have a self-consistent description of electronic states with multiple order parameters.
密度汎関数法は相転移の理論である。LevyとLiebが与えたユニバーサルエネルギー汎関数は絶対零度において厳密に定義されたランダウ・自由エネルギーである。一粒子密度はこの理論の第一秩序変数を与える。この講演では、コーン・シャム法の多配置参照型拡張が、複数の秩序変数をもつ電子状態の記述を与えることを示す。
【Contact】Dr. Yoshitaka Tateyama(館山佳尚)
Localized molecular orbital approach to the refractive index and nonlinear optical susceptibility : an ab initio calculation
局在化分子軌道を用いた(非)線形光学特性の第１原理計算
Dr. Shigeru Suehara(末原 茂博士)
【Date & Time】18 July 2007 (Wed), 3:30 pm - 5:00 pm
【Place】6F seminar room, Sengen site
【Speaker】Dr. Shigeru Suehara(末原 茂博士)
【Affiliation】First-Principles Simulation group (II), NIMS-CMSC(NIMS-CMSC 第一原理反応G)
【Title】Localized molecular orbital approach to the refractive index and nonlinear optical susceptibility : an ab initio calculation
局在化分子軌道を用いた(非)線形光学特性の第１原理計算
【Abstract】
A new hyperpolarizability calculation method based on bond-dipole moment has been developed. Since this method expresses (non)linear response properties in terms of localized molecular orbitals, it offers a chemically intuitive way of explaining these properties. In this seminar, we will introduce this method and present an approach to the origin of nonlinear optical properties of the typical glass forming materials within a classical "electron pair" picture.
化学の授業で最初に習う化学結合の”電子対”の描像を保ったまま、物質の(非)線形光学特性を求めることができれば、その特性を化学結合の観点から理解し、新たな高光学特性をもつ物質の探索研究に何らかの指針を与えることができるかもしれない。本講演では、局在化分子軌道によって表現された各々の”電子対”のもつBond-dipoleの電場に対する非線形応答を第１原理分子軌道法を用いて求める方法を紹介する。また、本手法の応用例として、一般的な(光学)ガラス形成物質の屈折率、第3次非線形感受率の計算結果を示す。
【Contact】Dr. Taizo Sasaki (佐々木泰造)
【Place】6F seminar room, Sengen site
【Speaker】Dr. Shigeru Suehara(末原 茂博士)
【Affiliation】First-Principles Simulation group (II), NIMS-CMSC(NIMS-CMSC 第一原理反応G)
【Title】Localized molecular orbital approach to the refractive index and nonlinear optical susceptibility : an ab initio calculation
局在化分子軌道を用いた(非)線形光学特性の第１原理計算
【Abstract】
A new hyperpolarizability calculation method based on bond-dipole moment has been developed. Since this method expresses (non)linear response properties in terms of localized molecular orbitals, it offers a chemically intuitive way of explaining these properties. In this seminar, we will introduce this method and present an approach to the origin of nonlinear optical properties of the typical glass forming materials within a classical "electron pair" picture.
化学の授業で最初に習う化学結合の”電子対”の描像を保ったまま、物質の(非)線形光学特性を求めることができれば、その特性を化学結合の観点から理解し、新たな高光学特性をもつ物質の探索研究に何らかの指針を与えることができるかもしれない。本講演では、局在化分子軌道によって表現された各々の”電子対”のもつBond-dipoleの電場に対する非線形応答を第１原理分子軌道法を用いて求める方法を紹介する。また、本手法の応用例として、一般的な(光学)ガラス形成物質の屈折率、第3次非線形感受率の計算結果を示す。
【Contact】Dr. Taizo Sasaki (佐々木泰造)
Spinons in spatially anisotropic frustrated antiferromagnets
空間的異方性をもつフラストレートした反強磁性体におけるスピノン励起
Dr. Masanori Kohno(河野昌仙博士)
【Date & Time】11 July 2007 (Wed), 3:30 pm - 5:00 pm
【Place】6F seminar room, Sengen site
【Speaker】Dr. Masanori Kohno(河野昌仙博士)
【Affiliation】Strong-Coupling Modeling group, NIMS-CMSC(NIMS-CMSC 強相関モデリングG)
【Title】Spinons in spatially anisotropic frustrated antiferromagnets
空間的異方性をもつフラストレートした反強磁性体におけるスピノン励起
【Abstract】
Spinons, which are characteristic excitation of one-dimensional systems, have recently been suggested in two-dimensional frustrated antiferromagnets. We explore this possibility through investigation of spatially anisotropic frustrated antiferromagnets using exact results on one-dimensional Heisenberg chains. We find three distinctive spectral features depending on the momentum: (1) one-dimensional spinons which are little influenced by interchain interactions, (2) bound states of spinons, and (3) incoherent excitations. Various unusual features observed in Cs2CuCl4, which can be regarded as an antiferromagnet on a spatially anisotropic triangular lattice, are consistently explained within the framework of the present approach with few adjustable parameters.
M. Kohno, O. A. Starykh, and L. Balents, cond-mat:0706.2012.
１次元系の素励起として知られているスピノンが、２次元のフラストレーションの強い系でも現れる可能性が、近年示唆されてきている。そこで、我々は空間的な異方性をもつフラストレートした反強磁性体を考え、1次元の厳密解を用いてその実現性について調べた。その結果、波数領域に応じて、動的性質に次の3種類の特徴的な振る舞いが現れることがわかった。（１）1次元のスピノンがほぼそのまま残った状態、（２）スピノンの結合状態、（３）インコヒーレントな励起である。これらにより、空間的異方性をもつ三角格子とみなせるCs2CuCl4で観測された様々な不可解な動的振る舞いを、ほとんどフィッティングパラメータなしで矛盾なく説明することに成功した。
【Contact】Dr. Yoshitaka Tateyama(館山佳尚)
【Place】6F seminar room, Sengen site
【Speaker】Dr. Masanori Kohno(河野昌仙博士)
【Affiliation】Strong-Coupling Modeling group, NIMS-CMSC(NIMS-CMSC 強相関モデリングG)
【Title】Spinons in spatially anisotropic frustrated antiferromagnets
空間的異方性をもつフラストレートした反強磁性体におけるスピノン励起
【Abstract】
Spinons, which are characteristic excitation of one-dimensional systems, have recently been suggested in two-dimensional frustrated antiferromagnets. We explore this possibility through investigation of spatially anisotropic frustrated antiferromagnets using exact results on one-dimensional Heisenberg chains. We find three distinctive spectral features depending on the momentum: (1) one-dimensional spinons which are little influenced by interchain interactions, (2) bound states of spinons, and (3) incoherent excitations. Various unusual features observed in Cs2CuCl4, which can be regarded as an antiferromagnet on a spatially anisotropic triangular lattice, are consistently explained within the framework of the present approach with few adjustable parameters.
M. Kohno, O. A. Starykh, and L. Balents, cond-mat:0706.2012.
１次元系の素励起として知られているスピノンが、２次元のフラストレーションの強い系でも現れる可能性が、近年示唆されてきている。そこで、我々は空間的な異方性をもつフラストレートした反強磁性体を考え、1次元の厳密解を用いてその実現性について調べた。その結果、波数領域に応じて、動的性質に次の3種類の特徴的な振る舞いが現れることがわかった。（１）1次元のスピノンがほぼそのまま残った状態、（２）スピノンの結合状態、（３）インコヒーレントな励起である。これらにより、空間的異方性をもつ三角格子とみなせるCs2CuCl4で観測された様々な不可解な動的振る舞いを、ほとんどフィッティングパラメータなしで矛盾なく説明することに成功した。
【Contact】Dr. Yoshitaka Tateyama(館山佳尚)
Quantum Monte-Carlo Study of Mn and Mn-oxide clusters
マンガン・マンガン酸化物の量子モンテカルロ計算
Dr. Hiori Kino(木野日織博士)
【Date & Time】13 June 2007 (Wed), 3:30 pm - 5:00 pm
【Place】8F larger seminar room, Sengen site
【Speaker】Dr. Hiori Kino(木野日織博士)
【Affiliation】First-Principles Simulation group (I), NIMS-CMSC(NIMS-CMSC 第一原理物性G)
【Title】Quantum Monte-Carlo Study of Mn and Mn-oxide clusters
マンガン・マンガン酸化物の量子モンテカルロ計算
【Abstract】
Many molecules and clusters of Mn and Mn-oxide have not only interesting physical properties but also can be found in enzymes as important components in biochemical reactions. The electronic structure calculations of these systems are difficult and, for example, choice of exchange-correlation functionals in Density Functional Theory can significantly influence both ground state geometries and spin-state predictions. Therefore, highly accurate calculation is very desirable for these systems. Experimentally, it is established that the Mn dimer is a van der Waals system with weak binding, however, the spin multiplicity has not been settled unambiguously with possibilities covering a range from singlet, triplet, etc, up to 2S+1=11. On the other hand, MnnOn molecules are quite well understood as being a high-spin system, but their geometries depend on the exchange-correlation functionals. We will present our recent results from the fixed-node quantum Monte Carlo calculations of these systems.
【Contact】Dr. Yoshitaka Tateyama(館山佳尚)
【Place】8F larger seminar room, Sengen site
【Speaker】Dr. Hiori Kino(木野日織博士)
【Affiliation】First-Principles Simulation group (I), NIMS-CMSC(NIMS-CMSC 第一原理物性G)
【Title】Quantum Monte-Carlo Study of Mn and Mn-oxide clusters
マンガン・マンガン酸化物の量子モンテカルロ計算
【Abstract】
Many molecules and clusters of Mn and Mn-oxide have not only interesting physical properties but also can be found in enzymes as important components in biochemical reactions. The electronic structure calculations of these systems are difficult and, for example, choice of exchange-correlation functionals in Density Functional Theory can significantly influence both ground state geometries and spin-state predictions. Therefore, highly accurate calculation is very desirable for these systems. Experimentally, it is established that the Mn dimer is a van der Waals system with weak binding, however, the spin multiplicity has not been settled unambiguously with possibilities covering a range from singlet, triplet, etc, up to 2S+1=11. On the other hand, MnnOn molecules are quite well understood as being a high-spin system, but their geometries depend on the exchange-correlation functionals. We will present our recent results from the fixed-node quantum Monte Carlo calculations of these systems.
【Contact】Dr. Yoshitaka Tateyama(館山佳尚)
First principles all-electron calculations for excited states of isolated systems using ring and ladder approximation
リングおよび梯子近似による孤立系の励起状態に対する第一原理全電子計算
Dr. Yoshifumi Noguchi(野口良史博士)
【Date & Time】10 May 2007 (Thur), 3:30 pm - 5:00 pm
【Place】6F seminar room, Sengen site
【Speaker】Dr. Yoshifumi Noguchi(野口良史博士)
【Affiliation】First-Principles Simulation group (II), NIMS-CMSC(NIMS-CMSC 第一原理反応G)
【Title】First principles all-electron calculations for excited states of isolated systems using ring and ladder approximation
リングおよび梯子近似による孤立系の励起状態に対する第一原理全電子計算
【Abstract】
Green’s function method beyond the framework of density functional theory is one of the most efficient methods to accurately treat the excited states of real systems. Particularly, GW approximation (GWA) in which a one-particle self energy operator is approximated as a product of the one-particle Green's function G and the dynamically screened Coulomb interaction W expressed as the ring diagrams up to the infinite order, can accurately estimate a one-electron excited energy. Recently, I applied the spin-polarized GWA to Alkali-metal clusters. In this talk, I will also introduce the ladder approximation (T-matrix) and analyze the Auger spectra of hydrocarbon systems evaluated by T-matrix.
密度汎関数理論の枠組みを超えたグリーン関数法は、現実の物質の励起状態を正確に取り扱うことができる非常に有効な手法である。特に、自己エネルギー演算子を１粒子グリーン関数Gと無限次までのリング図形によって展開された動的遮蔽クーロン相互作用Wの積で表すGW近似は、１電子励起エネルギーの計算に用いられ、成功を収めている。近年、私はスピン分極GW近似をアルカリ金属クラスターへ適応した。また本講演では、新しい計算手法である梯子近似（T-matrix）を紹介し、T-matrixにより求めた炭素化合物のオージェスペクトルも議論する予定である。
【Contact】Dr. Igor Solovyev
【Place】6F seminar room, Sengen site
【Speaker】Dr. Yoshifumi Noguchi(野口良史博士)
【Affiliation】First-Principles Simulation group (II), NIMS-CMSC(NIMS-CMSC 第一原理反応G)
【Title】First principles all-electron calculations for excited states of isolated systems using ring and ladder approximation
リングおよび梯子近似による孤立系の励起状態に対する第一原理全電子計算
【Abstract】
Green’s function method beyond the framework of density functional theory is one of the most efficient methods to accurately treat the excited states of real systems. Particularly, GW approximation (GWA) in which a one-particle self energy operator is approximated as a product of the one-particle Green's function G and the dynamically screened Coulomb interaction W expressed as the ring diagrams up to the infinite order, can accurately estimate a one-electron excited energy. Recently, I applied the spin-polarized GWA to Alkali-metal clusters. In this talk, I will also introduce the ladder approximation (T-matrix) and analyze the Auger spectra of hydrocarbon systems evaluated by T-matrix.
密度汎関数理論の枠組みを超えたグリーン関数法は、現実の物質の励起状態を正確に取り扱うことができる非常に有効な手法である。特に、自己エネルギー演算子を１粒子グリーン関数Gと無限次までのリング図形によって展開された動的遮蔽クーロン相互作用Wの積で表すGW近似は、１電子励起エネルギーの計算に用いられ、成功を収めている。近年、私はスピン分極GW近似をアルカリ金属クラスターへ適応した。また本講演では、新しい計算手法である梯子近似（T-matrix）を紹介し、T-matrixにより求めた炭素化合物のオージェスペクトルも議論する予定である。
【Contact】Dr. Igor Solovyev
Application of fragment molecular orbital (FMO) method to nano-bio field
フラグメント分子軌道(FMO)法のバイオ・ナノ分野への応用
Dr. Tatsuya Nakano(中野達也博士)
【Date & Time】9 March 2007 (Fri), 1:30 pm - 3:00 pm
【Place】8F larger seminar room, Sengen site
【Speaker】Dr. Tatsuya Nakano(中野達也博士)
【Affiliation】National Institute of Health Sciences / IIS, University of Toky(国立医薬品食品衛生研究所／東京大学生産技術研究所)
【Title】Application of fragment molecular orbital (FMO) method to nano-bio field
フラグメント分子軌道(FMO)法のバイオ・ナノ分野への応用
【Abstract】
Kitaura et al. (Chem. Phys. Lett. 312, 319-324 (1999)) have proposed an ab initio fragment molecular orbital (FMO) method by which large molecules such as proteins can be easily treated with chemical accuracy. In the ab initio FMO method, a molecule or a molecular cluster is divided into M fragments, and the MO calculations on the fragments (monomers) and the fragment pairs (dimers) are performed to obtain the total energy that is expressed as a summation of the fragment energies and inter-fragment interaction energies (IFIEs). In this presentation, I will provide a brief description of the ab initio FMO method and demonstrate recent applications in nano-bio field.
1999年に北浦らにより提唱されたフラグメント分子軌道(FMO)法は、分子系をフラグメントに分割し、フラグメントのモノマー、ダイマー、トリマー・・・の計算から系全体を計算する方法であり、タンパク質やDNAのような巨大分子系全体を量子論的に扱う計算方法として、近年注目を集めている。今回の発表では、FMO法の概要と、バイオ・ナノ分野におけるFMO法の応用について紹介したい。
【Contact】Dr. Jun Nara (奈良純)
【Place】8F larger seminar room, Sengen site
【Speaker】Dr. Tatsuya Nakano(中野達也博士)
【Affiliation】National Institute of Health Sciences / IIS, University of Toky(国立医薬品食品衛生研究所／東京大学生産技術研究所)
【Title】Application of fragment molecular orbital (FMO) method to nano-bio field
フラグメント分子軌道(FMO)法のバイオ・ナノ分野への応用
【Abstract】
Kitaura et al. (Chem. Phys. Lett. 312, 319-324 (1999)) have proposed an ab initio fragment molecular orbital (FMO) method by which large molecules such as proteins can be easily treated with chemical accuracy. In the ab initio FMO method, a molecule or a molecular cluster is divided into M fragments, and the MO calculations on the fragments (monomers) and the fragment pairs (dimers) are performed to obtain the total energy that is expressed as a summation of the fragment energies and inter-fragment interaction energies (IFIEs). In this presentation, I will provide a brief description of the ab initio FMO method and demonstrate recent applications in nano-bio field.
1999年に北浦らにより提唱されたフラグメント分子軌道(FMO)法は、分子系をフラグメントに分割し、フラグメントのモノマー、ダイマー、トリマー・・・の計算から系全体を計算する方法であり、タンパク質やDNAのような巨大分子系全体を量子論的に扱う計算方法として、近年注目を集めている。今回の発表では、FMO法の概要と、バイオ・ナノ分野におけるFMO法の応用について紹介したい。
【Contact】Dr. Jun Nara (奈良純)
First principles molecular dynamics simulations of electrochemical reactions
電気化学反応の第一原理分子動力学シミュレーション
Dr. Minoru Ohtani(大谷実博士)
【Date & Time】21 February 2007 (Wed), 3:30 pm - 5:00 pm
【Place】8F larger seminar room, Sengen site
【Speaker】Dr. Minoru Ohtani(大谷実博士)
【Affiliation】Institute for Solid State Physics, University of Toky(東京大学物性研究所)
【Title】First principles molecular dynamics simulations of electrochemical reactions
電気化学反応の第一原理分子動力学シミュレーション
【Abstract】
In surface science, because of computational efficiency and tractability, first-principles calculations often use the slab model in which layers of atoms and a vacuum region are periodically repeated. Due to the periodic boundary condition, the slab model is well-known to have the difficulty in handling charged or polarized surfaces. To overcome this, we have developed a new calculation method called effective screening medium (ESM) method. In this seminar I will present details of the ESM method and some recent results for electrochemical reactions.
表面化学において、計算効率や扱いやすさから第一原理計算ではスラブモデルが利用される。スラブモデルでは真空をスラブで挟んだ構造が繰り返されるが、周期境界条件を課す為に、極性表面や荷電表面を扱うことが困難であった。我々はこの困難を克服する為に有効遮蔽体(ESM)法を提案した。荷電表面を直接扱うことにより、電極表面で起こる電気化学反応も直接計算が可能になった。講演ではESM法の詳細を紹介し、最近の電気化学反応系への適用例を紹介する。
【Contact】Dr. Yoshitaka Tateyama(館山佳尚)
【Place】8F larger seminar room, Sengen site
【Speaker】Dr. Minoru Ohtani(大谷実博士)
【Affiliation】Institute for Solid State Physics, University of Toky(東京大学物性研究所)
【Title】First principles molecular dynamics simulations of electrochemical reactions
電気化学反応の第一原理分子動力学シミュレーション
【Abstract】
In surface science, because of computational efficiency and tractability, first-principles calculations often use the slab model in which layers of atoms and a vacuum region are periodically repeated. Due to the periodic boundary condition, the slab model is well-known to have the difficulty in handling charged or polarized surfaces. To overcome this, we have developed a new calculation method called effective screening medium (ESM) method. In this seminar I will present details of the ESM method and some recent results for electrochemical reactions.
表面化学において、計算効率や扱いやすさから第一原理計算ではスラブモデルが利用される。スラブモデルでは真空をスラブで挟んだ構造が繰り返されるが、周期境界条件を課す為に、極性表面や荷電表面を扱うことが困難であった。我々はこの困難を克服する為に有効遮蔽体(ESM)法を提案した。荷電表面を直接扱うことにより、電極表面で起こる電気化学反応も直接計算が可能になった。講演ではESM法の詳細を紹介し、最近の電気化学反応系への適用例を紹介する。
【Contact】Dr. Yoshitaka Tateyama(館山佳尚)
Molecular adsorption, foreign atom incorporation, and the formation of superstructures on Si(001)
Prof. Hanchul Kim
【Date & Time】1 February 2007 (Thur), 3:30 pm - 4:30 pm
【Place】6F seminar room, Sengen site
【Speaker】Prof. Hanchul Kim
【Affiliation】Korea Research Institute of Standards and Science
【Title】Molecular adsorption, foreign atom incorporation, and the formation of superstructures on Si(001)
【Abstract】
The Si(001) surface constitutes the most important substrate in the current semiconductor industry, and the decreasing size of the devices demand to develop the atomic-scale controllability. A prerequisite for such an atomic level control is to understand the behavior of the foreign atoms near the surface. In this presentation, I would like to describe a comprehensive understanding on the behavior of carbon atoms, which is achieved by the ab initio pseudopotential total energy calculations and verified by high-resolution scanning tunneling microscopy experiments. The adsorption of small molecules on Si(001) seems to be an apparently easy problem, and has been believed to be fully understood in many cases. Our studies on acetylene (C2H2) and ammonia (NH3) molecules demonstrate that the adsorption structures have only been partly understood. The existence of dimers on Si(001) makes the problem more versatile, and there are multiple adsorption configurations. The adsorbed molecules may be used as a source of foreign atoms upon an appropriate thermal treatment. The dissociated foreign atoms usually modifies the substrate and sometimes produce superstructures on Si(001). In the second half, I would like to focus on the carbon-induced modification of Si(001) and the identification of the atomic structure of the carbon-induced superstructures: 2 xn and c(4 x4). Our study lessons that a careful and accurate investigation is necessary to understand the atomic processes, which is a prerequisite for developing the atomic level controllability.
【Contact】Dr. Taizo Sasaki (佐々木泰造)
【Place】6F seminar room, Sengen site
【Speaker】Prof. Hanchul Kim
【Affiliation】Korea Research Institute of Standards and Science
【Title】Molecular adsorption, foreign atom incorporation, and the formation of superstructures on Si(001)
【Abstract】
The Si(001) surface constitutes the most important substrate in the current semiconductor industry, and the decreasing size of the devices demand to develop the atomic-scale controllability. A prerequisite for such an atomic level control is to understand the behavior of the foreign atoms near the surface. In this presentation, I would like to describe a comprehensive understanding on the behavior of carbon atoms, which is achieved by the ab initio pseudopotential total energy calculations and verified by high-resolution scanning tunneling microscopy experiments. The adsorption of small molecules on Si(001) seems to be an apparently easy problem, and has been believed to be fully understood in many cases. Our studies on acetylene (C2H2) and ammonia (NH3) molecules demonstrate that the adsorption structures have only been partly understood. The existence of dimers on Si(001) makes the problem more versatile, and there are multiple adsorption configurations. The adsorbed molecules may be used as a source of foreign atoms upon an appropriate thermal treatment. The dissociated foreign atoms usually modifies the substrate and sometimes produce superstructures on Si(001). In the second half, I would like to focus on the carbon-induced modification of Si(001) and the identification of the atomic structure of the carbon-induced superstructures: 2 xn and c(4 x4). Our study lessons that a careful and accurate investigation is necessary to understand the atomic processes, which is a prerequisite for developing the atomic level controllability.
【Contact】Dr. Taizo Sasaki (佐々木泰造)
Dynamics of driven systems - mode locking, symmetry breaking, and resonance
Prof. Moo Young Choi
【Date & Time】25 January 2007 (Thur), 10:00 am - 11:00 am
【Place】6F seminar room, Sengen site
【Speaker】Prof. Moo Young Choi
【Affiliation】Department of Physics, Seoul National University
【Title】Dynamics of driven systems - mode locking, symmetry breaking, and resonance
【Abstract】
A many-particle system under external drive may display rich dynamic behaviors such as mode locking, dynamic transition, and resonance.
As a physically realizable example, we consider frustrated arrays of superconducting junctions driven by currents. At zero temperature the mode locking phenomena is manifested by giant Shapiro steps in the current-voltage characteristics.
Melting of these steps due to thermal fluctuations is accompanied by a dynamic transition to the disordered state. Also discussed are the characteristic stochastic resonance behavior and vortex motion in response to the driving currents.
【Contact】Dr. Xiao Hu (胡暁)
【Place】6F seminar room, Sengen site
【Speaker】Prof. Moo Young Choi
【Affiliation】Department of Physics, Seoul National University
【Title】Dynamics of driven systems - mode locking, symmetry breaking, and resonance
【Abstract】
A many-particle system under external drive may display rich dynamic behaviors such as mode locking, dynamic transition, and resonance.
As a physically realizable example, we consider frustrated arrays of superconducting junctions driven by currents. At zero temperature the mode locking phenomena is manifested by giant Shapiro steps in the current-voltage characteristics.
Melting of these steps due to thermal fluctuations is accompanied by a dynamic transition to the disordered state. Also discussed are the characteristic stochastic resonance behavior and vortex motion in response to the driving currents.
【Contact】Dr. Xiao Hu (胡暁)