講師：Tatsuya Ishiyama (石山 達也氏) (Graduate School of Science and Engineering, University of Toyama
)
題目：Molecular Dynamics Study of Structure and Spectroscopy at Liquid Interface
要旨：
Liquid interfaces are ubiquitous and of fundamental importance in many physicochemical phenomena,
such as atmospheric reactions on aerosol particles, cavitation bubbles, biochemical reactions, and
so forth. The interfacial region is very limited in space and has unique properties compared to the
bulk due to its heterogeneous environment. Molecular simulation is a powerful technique to elucidate
and predict physical and chemical properties of interfaces with thickness of nm order. In this talk,
we focus on the recent progresses of the simulation studies of molecular structure, vibrational
spectroscopy at the interfacial region. A key experimental technique to elucidate interfacial
molecular structure is the interface-selective vibrational sum frequency generation (VSFG)
spectroscopy. A close collaboration of VSFG studies with molecular simulation has opened an avenue
for understanding new aspects of the structures of aqueous surfaces. We introduce a basic theory of
VSFG and discuss molecular structures of aqueous surfaces depicted from VSFG spectroscopy.
日時：2015年12月8日（火）13:00-
場所：理学部5号館401号室
講師：Itsuo Hanasaki (花崎 逸雄氏) (Tokyo University of Agriculture and Technology)
題目：Applied statisitical mechanics for engineering: from molecular dynamics and coarse-graining
to big data analysis of fluctuation measurements and single-particle characterization
要旨：
Ubiquity and importance of thermal fluctuation in nanotechnology is obvious from the typical spatio-temporal
scales of interest and the central limit theorem. However, its consequence is not fully recognized in the
engineering fields, and they are far from fully exploited in spite of the epoch-making advances in the statistical
mechanics in the recent decades. Applied mechanics is not merely an application of the fundamentals, but it
requires deep and sharp appreciation of both science and technology in a sensible manner: Recent trend of strong
emphasis on the “innovation” in the academia as well as industries sheds light on the essential role of the
applied mechanics that has not been fully appreciated. I would like to introduce some of my work with an emphasis
on the viewpoints of statistical mechanics and dynamical systems while they are not always explicitly manifested.
The time-series introduction of the specific topics hopefully conveys the idea of this ongoing journey for the creative
combination of science and technology.
日時：2015年11月17日（火）13:00-
場所：理学部5号館401号室
講師：Tsuyoshi Yamaguchi (山口 毅氏) (Nagoya University)
題目：Theory on dynamics of electrolyte solutions: Interplay between dynamics of bound pairs and ionic atmosphere
要旨：
Transport properties of electrolyte solutions, such as ionic conductivity, viscosity and ultrasonic absorption, are dynamic
quantities of both academic and industrial importance. The dynamics of electrolyte solution is characterized by the
influence of strong Coulombic interaction between ions, which makes it different from the dynamics of liquids composed
of neutral molecules.
There are two different effects of the Coulombic interaction on the dynamics of electrolyte solutions. The first one is
the ionic association, and the second one is the ionic atmosphere. The strong attraction between a cation and an anion makes
them bound to each other in weakly polar solvents, leading to the formation of a neutral molecule, called "ion pair". On the
other hand, a diffuse distribution of counter ion, called "ionic atmosphere", is formed around an ion due to the long-range
nature of the Coulombic interaction. These two effects have been treated separately in traditional theories, although they
work simultaneously in real solutions.
In this work, we developed a theory that can calculate transport coefficients from the pair distribution functions between ions
without introducing the association species a priori [1,2]. The theory can describe both the bound dynamics of ion pairs and the
collective long-range dynamics related to the ionic atmosphere.
The theory was first applied to the ultrasonic absorption [1,3]. Our theoretical calculation reproduced the bimodal relaxation
often observed in experiments. The slower mode was ascribed to the association dynamics of CIP as had been proposed by the conventional
model. On the other hand, the faster mode was assigned to the collective dynamics in our calculation.
The theory was then applied to the ionic conductivity [2,4]. The effects of the interionic interaction on ionic conductivity were divided
into the contributions of the pair distributions of ions at various interionic distances. It was demonstrated that the lifetime of
CIP must be much longer than its reorientational relaxation time in order for all the pairs of contact ions to be regarded as CIP in
conductometry. An extension of the theory to include the hydrodynamic interaction between ions was also proposed, and applied to the
ionic conductivity of the aqueous solution of NaCl [4].
References
[1] T. Yamaguchi, T. Matsuoka, and S. Koda, J. Chem. Phys., 126(14), 144505 (2007).
[2] T. Yamaguchi, T. Matsuoka, and S. Koda, J. Chem. Phys., 127(6), 064508 (2007).
[3] T. Yamaguchi, T. Matsuoka, and S. Koda, J. Chem. Phys., 127(23), 234501 (2007).
[4] T. Yamaguchi, T. Matsuoka, and S. Koda, J. Chem. Phys., 130(9), 094506 (2009).
日時：2015年11月13日（金）17:00-
場所：理学部5号館401号室
講師：Kyohei Takae (高江 恭平氏) (University of Tokyo)
題目：Water in a Capacitor: Structure, Fluctuation, and Response
要旨：
The dielectric response of condensed matter is often studied under
the assumption that the external electric field is a controllable parameter.
However, it is needed to solve the Poisson equation under an appropriate
boundary condition to obtain the macroscopic electric field, because it
depends on the polarization of the system. We construct a method of
molecular simulation for calculating the electrostatic interactions
among charged particles between parallel metallic plates [1].
By applying this method, we study structure and dynamics of water in a
capacitor [2,3]. Image interaction arising from the dielectric discontinuity
at the interface induces polarization near the surface, which decreases
the bulk electric field. Homogeneous correlation of polarization fluctuation
emerges in this geometry. Next we discuss the relationship between macroscopic
electric field and local electric field exerted on each molecule, where the
latter is considerably larger than the former. The orientation of water
dipole is almost parallel to the local electric field, and small fluctuation
is relaxed by the librational motions. We also discuss responses of water
molecules after sudden change of potential difference, where collective
reorientation is observed.
references
[1] K. Takae and A. Onuki, J. Chem. Phys. 139, 124108 (2013).
[2] K. Takae and A. Onuki, J. Phys. Chem. B 119, 9377 (2015).
[3] K. Takae and A. Onuki, J. Chem. Phys. 143, 154503 (2015).
日時：2015年6月16日（火）13:00-
場所：理学部5号館401号室
講師：Takuya Sugimoto (Graduate School of Life and Environmental Sciences, University of Tsukuba)
題目：Aggregation Rates of Charged Colloidal Particles in a Couette Flow: Trajectory Analysis with Non-linear Poisson-Boltzmann Solution
講師：Hayato Shiba （芝 隼人）(The University of Tokyo)
題目：Membrane simulation - elasticity, surface tension, and some applications
要旨：
Based on coarse-grained simulations of membrane models,
I would like to talk about the following issues.
(i) Structure formation of surfactant membrane
Coarse-grained simulations have been a powerful tool for simulations of
soft matter on micrometer scales. In order to address structure formation
of surfactant membranes under shear flow, we employ the meshless membrane
model. It realises topological changes (e.g. rupture and reconnections) of
membrane surfaces and is highly coarse-grained, so that we can treat large-scale
defect dynamics underlying multilamellar membranes. [1]
(ii) Membrane elasticity and residual tension
Using the above coarse-grained model, I will talk about the systematic
way in which we can asses the "true" value of the bending rigidity, based on
the knowledge on the wavenumber dependence[2]. In addition, we would like
to address "residual surface tension" problem on a stress-free membrane [3].
[1] Hayato Shiba, Hiroshi Noguchi and Gerhard Gompper, JCP 139, 014702/1-11 (2013).
[2] Hayato Shiba and Hiroshi Noguchi, PRE 84, 031926/1-13 (2011).
[3] Hayato Shiba, Hiroshi Noguchi, and Jean-Baptiste Fournier, to be submitted (2015).