ISSN:
0020-7608
Schlagwort(e):
Computational Chemistry and Molecular Modeling
;
Atomic, Molecular and Optical Physics
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
Notizen:
Extensional elastic moduli have been calculated for several organic high polymers based on the modified neglect of diatomic overlap (MNDO) Hamiltonian. Standard semiempirical methods, by application of the Born-von Karman boundary conditions, can be used to calculate heats of formation of polymer chain sections, or computational unit cells, called clusters. Unit cell heats of formation at elongated translation vectors, combined with experimental or estimated densities, allow for the calculation of elastic moduli. Two potential sources of error were identified: (a) finite geometry optimization can result in pseudorandom errors in the calculated heat of formation, and (b) anharmonic distortion can become significant at large strains. Errors due to both causes can typically be minimized if strains between 3 and 10% are selected. As expected, the calculated moduli, although higher than those observed experimentally, agree with longitudinal values for perfectly oriented systems.
Zusätzliches Material:
4 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/qua.560300746
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