Papers by Author: Shigenobu Ogata

Abstract: CuxZr1-x (x=0.30~0.85) binary amorphous alloy models were constructed using molecular dynamics simulations. In order to characterize the short-ranged local structures and the free volume of the whole cell, Voronoi polyhedral analyses were performed for their initial states and also for the deformed states. Both geometrical and physical factors are intimately related to each other and exhibit a large influence on mechanical properties. The elastic properties of shear modulus and bulk modulus tend to increase as the free volume decreases. The Poisson’s ratio, which is related to the glass fragility, increases as the free volume. However, the relation among three elastic properties obtained from the continuous mechanics of the isotropic body does not hold. Also, the maximum stress in the finite deformation drastically decreases with increasing free volume content.

Abstract: Process of a silica cluster on a polyimide surface was simulated by atomistic calculations combining the semi-empirical molecular orbital method and algorithms that can find the optimal path of a chemical bonding process. Specifically, we estimated the activation and sorption energies in the process. From the simulations, we found that chemical bonding occurs between a silica cluster and the polyimide substrate surface. In the adsorption processes, those reactions between the silica cluster and the polyimide surface which involve Si-O bonding between the cluster and the polyimide are the most probable.