Hybrid particles, molecular level

A molecular level mixed-hybrid particle has been prepared by a one-step procedure in our laboratory . An organic domain in hybrid particles was achieved by adding methyltriethoxysilane (MTEOS) to an alcohol/water/ammonia solution and shaking for 24 hours. Fine particles (2-3 Jm) were obtained with narrow polydispersity. Using a similar procedure with chloromethylphenylsiloxane (COPTOS), we were unsuccessful in producing stable particles. 

The approach with the partitioning of the system into a QM and a classical molecular mechanical (MM) part, thus usually termed hybrid QM/MM procedure, provides a reasonable reduction of the computational effort by restricting the time-consuming QM calculation of forces to the most relevant part of the liquid system. The main error sources in this approach are a too small choice of the QM region, an inadequate level of theory for the QM calculation, the choice of suitable potentials for the MM part of the system, and smooth transitions of particles between QM and MM region. In conventional QM/MM procedures, the whole system is first evaluated at MM level and then corrected by the QM data. This means that classical potential functions (with all their problems and difficulty of construction) are needed for all components of the system. A recently developed methodology can reduce the need for such potentials to the solvent only, as will be outlined below. 

I believe essentially all of the material in the first five chapters is accessible to the advanced general chemistry students at most universities. The final three chapters are written at a somewhat higher level on the whole. Chapter 6 introduces Schrodinger s equation and rationalizes more advanced concepts, such as hybridization, molecular orbitals, and multielectron atoms. It does the one-dimensional particle-in-a-box very thoroughly (including, for example, calculating momentum and discussing nonstation-ary states) in order to develop qualitative principles for more complex problems. 

The hydration of metal ions is a process that belongs to what we call the acid-base reaction in chemistry. The acid-base reaction involves no electron transfer between separate partners but a localized electron rearrangement to make up or break down a hybrid molecular orbital between an acid particle and a base particle, that is, the formation or the dissolution of a bonding molecular orbital due to the interaction between the frontier donor orbital of a particle Lewis base) and the frontier acceptor orbital of another particle Lewis acid). In order for an acid-base reaction to occur between a base particle and an acid particle, the electronic energy levels of the frontier orbitals for both acid and base particles are required to be close enough to each other for the orbital hybridization to prevail [3]. 

MD simulations require the description of the interactions between the particles (potential function, or a force field) of a molecular system [27]. The potential function can be defined on various levels. The most conunonly adopted potential functions in chemistry and biology are based on molecular mechanics (MM), with a classical treatment of particle-particle interactions. With well-chosen parameter sets, these potential functions can reproduce structural and conformational changes in systems, except chemical reactions. The analytic forms of the potential functions, which involve low computational cost, make it possible for MD simulations to include a huge number of atoms. When potentials based on quantum mechanics (QM) are adopted, MD simulations can give finer levels of detail, such as chemical reactions and electronic structures, but expensive computational costs are involved simultaneously. As a compromise, hybrid QM/MM approaches are... 

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