Dynamics of complex condensed systems

Abstract

The following subjects were investigated: (1) dynamics of three dimension cellular pattern growth. An effective computer modeling of time-evolution of three-dimensional cellular systems like soap froths and crystalline grain aggregates was devised. Various results including topological characteristics of three-dimensional cellular patterns were obtained using a simpler version of derived vertex equations; (2) collective and local excitation in diluted antiferromagnetic Heisenberg systems. It was examined whether or not density of states for collective and local excitation in diluted antiferromagnetic Heisenberg systems was enhanced by thermal activation; (3) dynamics of shape deformation and in-plane phase separation of fluid membranes. In order to study influence of shape deformations on coarsening dynamics of phase separation, dynamics of the shape deformation and in-plane phase separation of fluid membranes was simulated by using a purely dissipative dynamical model of a two component vesicle; and (4) pressure induced amorphization of a molecular crystal SnI4. Study was made on a characteristic feature in common in thermobaric processes that solid state amorphization results in a phase less dense than crystalline phase which would form under equilibrium conditions. The system was modeled to be an assembly of rigid tetrahedra interacting with one another through van der Waals force between respective vertices.

ここでは4主題について研究した。(1)3次元セルラパターン成長の動力学。石鹸のあわや水晶粒の集合体のような3次元セルラ系の時間発展の有効な計算機模型化を考案した。導出したバーテックス方程式の簡単なバージョンを用いて3次元セルラ模型の位相特性を含む種々な結果を得た。(2)希釈にした反強磁性ハイゼンベルク系における集団および局所励起。希釈した反強磁性Heisenberg系における集団および局所励起の状態密度が熱運動によって増強するか否かを調べた。(3)流体薄膜の形状変形および面内相分離の動力学。相分離の粗大化動力学への形状変形の影響を調べるために、2成分ベシクルの純粋に散逸的な動力学模型を使って流体薄膜の形状変化と面内相分離の動力学をシミュレートした。(4)分子結晶SnI4の圧力誘起非晶質化。平衡条件下で形成される結晶相よりも密度の小さい相で固体の非晶質化が起こるという熱圧過程に共通の特徴を調べた。バーテックス間のファン・デル・ワールス力を通して相互作用する厳密な4面体の集合体で体系を模型化した。