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  • 1990-1994  (2)
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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 5477-5485 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In the present work we have studied the thermal isomerization process of polyacetylene (PA) from the trans-cisoid (TC) and cis-transoid (CT) forms to the trans-transoid (TT) form. We have used the molecular dynamics-modified neglect of diatomic overlap (MD-MNDO) method, which combines a molecular dynamics algorithm with the MNDO approximation. The thermal isomerization mechanism from TC-to-TT form is fully described. In our simulation, starting from the CT form in its ground state and heating the system up to T=450 K, there is no evidence of an isomerization process. However, a model, which simulate the subtraction of some charge from the double bonds of the PA chains, is able to give important insights into the isomerization mechanism from the CT to the TT form. This charge subtraction is essential to induce a CT-to-TC local transformation followed by the TC-to-TT isomerization.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 502-507 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We introduce an algorithm that couples the molecular dynamics (MD) method to the modified neglect of diatomic overlap (MNDO) approximation. This approach is applied to the study of the carbon clusters Cn with n ranging from 20 to 60. We calculate the relative stability of some well-known structures as polyacetylenic rings and fullerenes. The results obtained are in substantial agreement with calculations available in the literature. The main emphasis of the paper is on the possibility of finding, with our approach, new isomers starting from different initial configurations or after thermal excursions. For some values of n, new stable isomers are found. The results allow us also to give explanations of the observed low abundance in the mass spectra of the clusters with n ranging between 30 and 40 (the so-called "dead'' region).
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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