No abstract

No abstract

Layered ZnO microspheric particles were prepared by the thermal decomposition of layered hydrozincite (LZnHC), which was synthesized from zinc nitrate and urea in a water/PEG400 mixture. The influence of the starting reagents, their concentrations, and the amount of PEG in the water/PEG400 mixture on the particle growth was observed. The chemical aspect of the particle growth was proposed in the frame of the partial charge model (PCM), and the formation of [Zn(OH)(2)(OH(2))(4)](0) and [Zn(OH)(HCO(3))(OH(2))(3)](0) was predicted for the solid phase. The assumed growth mechanism, which follows the "nonclassical crystallization" concept of a self-assembling mechanism, was observed in situ by small-angle X-ray scattering (SAXS) and predicts the rapid formation of approximately 6 nm sized building units. The size of these nano building units, stable only in the reaction medium, remains nearly constant during the synthesis, as the concentration of the nano building units increases throughout the reaction. The nano building units connect into leaves of LZnHC with a thickness of 20 nm. These leaves of LZnHC are further agglomerated into porous, microsphere-like particles with sizes up to 4 μm.

An implicit Runge-Kutta (RK) integration scheme, the two-stage 4th order Gauss-Legendre Runge-Kutta (GLRK) method, for numerical solution of molecular dynamics equations is described. An estimate of the initial guess for the starting value of the fixed-point iteration is based on the typical particle frequency. The algorithm was applied to the harmonic oscillator and compared to various algorithms for numerical integration of equations of motion. The algorithm was also applied to a complex system of 256 particles interacting through a Lennard-Jones potential, and compared to a summed form of the Verlet algorithm. The proposed implicit RK method, which permits a wide range of time steps, is highly accurate and stable and is thus suitable for the molecular dynamics integration.

No abstract