Structural and Electronic Properties of Fluorinated and Chlorinated Polyacetylene
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- 作者：Michael Springborg
- 刊名：Journal of the American Chemical Society
- 出版年：1999
- 出版时间：December 8, 1999
- 年：1999
- 卷：121
- 期：48
- 页码：11211 - 11216
- 全文大小：120K
- 年卷期：v.121,no.48(December 8, 1999)
- ISSN：1520-5126
文摘
Using a density-functional method we have calculated the electronic and structural properties ofinfinite and periodic (CF)x, (CCl)x, and (CFCCl)x chains. Only for the (CF)x and (CCl)x trans isomers withouta C-C bond-length alternation we have optimized the structure completely and subsequently explored whetherthe total energy for these isomers could be lowered upon a such alternation. Finally, we studied the electronicproperties of different cis isomers with fixed structures as well as of trans and cis isomers of (CFCCl)x. Specialemphasis is put on whether these newly synthesized materials have properties resembling those of most otherconjugated polymers, i.e., whether 
orbitals from mainly carbon functions are those closest to the Fermi leveland whether a bond-length alternation exists. We find that the F-substituted materials in many respects aresimilar to the unsubstituted ones (with, however, smaller differences), but that the Cl-substituted ones differsignificantly from the unsubstituted ones. The trans isomers of the systems with mixed substitutions possessproperties that are intermediate between those of the F- and the Cl-substituted ones. On the other hand, the cisisomers of (CFCCl)x have markedly different properties and are the only ones with F/Cl nearest neighbors. Acomparison with the experimental information suggests that for (CFCCl)x the trans isomer is the one that issynthesized. Finally, we predict that only for (CF)x will solitons or polarons be generated upon doping.
orbitals from mainly carbon functions are those closest to the Fermi leveland whether a bond-length alternation exists. We find that the F-substituted materials in many respects aresimilar to the unsubstituted ones (with, however, smaller differences), but that the Cl-substituted ones differsignificantly from the unsubstituted ones. The trans isomers of the systems with mixed substitutions possessproperties that are intermediate between those of the F- and the Cl-substituted ones. On the other hand, the cisisomers of (CFCCl)x have markedly different properties and are the only ones with F/Cl nearest neighbors. Acomparison with the experimental information suggests that for (CFCCl)x the trans isomer is the one that issynthesized. Finally, we predict that only for (CF)x will solitons or polarons be generated upon doping.