Molecular glasses theoretical approaches

The need to model this distribution means that it is difficult to theoretically study the electronic states of oxide glasses. There are several ways to theoretically study the electronic state of oxide materials, these include band calculations and molecular orbital methods. (9-13) The randomness is a problem for the band approach because it requires translational symmetry of the unit cell a large super-cell may be chosen, but this is at the cost of increased computer time and possible spurious interactions between cells. On the other hand, the molecular orbital (MO) approach is usually applied to isolated molecules, (14-16) and can not handle infinite numbers of atoms as in the solid state. The embedded potential method is one of the improvements in moleculeir orbited methods which have been introduced in order to study solid state materials. (17) Basically, the cluster Hamilto-... 

Molecular dynamics calculations have been carried out to simulate a conformational model and vibrational spectra of poly(dichlorophospha-zenes). Molecular dynamics similations for [NP(OCH2CF3)2] and the isomers [NP(OBu")2] , [NP(OBu )2] and [NP(OBu )2] show a reasonable agreement between the calculated and experimental values of density and glass transition temperature as well as for gas transport parameters in these polymers.Small molecule models have been used for a theoretical approach of poly(thionylphosphazenes). ... 

Several approaches to the description of molecular entanglements in polymers are available at present. A brief outline will be given here. The best known is the version of the binary hook [9,10] with some network features. At temperatures (T) exceeding the temperature of glass transition (Tg) for the polymer, the network density V(,i, is usually determined in the framework of the rubber-like elasticity, while for Tentanglement network is proven both theoretically and... 

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