Density functional study of organic systems : molecules, polymers, and crystals

Montanari, B.

Dissertation / PhD Thesis/Book

Density functional study of organic systems : molecules, polymers, and crystals

Montanari, B. (Corresponding author)FZJ*

1999
Forschungszentrum, Zentralbibliothek Jülich

Jülich : Forschungszentrum, Zentralbibliothek, Berichte des Forschungszentrums Jülich 3624, (1999) = Köln, Univ., Diss., 1999

Please use a persistent id in citations: http://hdl.handle.net/2128/20261

Report No.: Juel-3624

Abstract: Density functional calculations have been performed on three polymeric systems, namely isotactic polypropylene ( it-PP), polyethylene (PE) and systems related to bisphenol-A polycarbonate (BPA-PC). The structure of an isolated chain of it-PP and of several of its segments ha.ve been optimized. The results a.gree well with experiment and show that the structural properties of the small molecules can be used to predict the energy surfaces of the infinite chain. The computation of the equilibrium structure of PE confirms the reliability of the method in the description of the intm-molecular interactions in hydrocarbons. Different approximations for the exchange-correlation energy have been tested to describe the weak inter-molecular interactions on two types of molecular crystals: crystalline PE and a crystalhne analog of BPA-PC. The local density approximation overestirnates the intermolecular bonds in both, and the Becke-Perdew functional gives no intermolecular binding in the former and a very weak bond in the latter. The functional of Perdew) Burke, and Ernzerhof leads to a. better description of the binding in both systems. The study of BPA-PC has then been extended to structural and vibrational properties of several fragments of the infinite chain. The calculation of the energy barriers for characteristic molecular motions provides insight into the relation between these properties and the intra- and inter-molecular arrangement. In order to extend the size and time scales of the calculations, all these results have been used to tune a classical force field, which has then been applied in Monte Carlo simulations of polycarbonate systems containing several thousa.nd atoms. The results concern bulk and surface properties of an amorphous system.

Note: Record converted from VDB: 12.11.2012
Note: Köln, Univ., Diss., 1999

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