Singlet Fission Rate: Optimized Packing of a Molecular Pair. Ethylene as a Model
The result's identifiers
Result code in IS VaVaI
<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F61388963%3A_____%2F19%3A00509382" target="_blank" >RIV/61388963:_____/19:00509382 - isvavai.cz</a>
Alternative codes found
RIV/68407700:21230/19:00333769 RIV/60461373:22340/19:43919956
Result on the web
<a href="https://pubs.acs.org/doi/10.1021/jacs.9b08173" target="_blank" >https://pubs.acs.org/doi/10.1021/jacs.9b08173</a>
DOI - Digital Object Identifier
<a href="http://dx.doi.org/10.1021/jacs.9b08173" target="_blank" >10.1021/jacs.9b08173</a>
Alternative languages
Result language
angličtina
Original language name
Singlet Fission Rate: Optimized Packing of a Molecular Pair. Ethylene as a Model
Original language description
A procedure is described for unbiased identification of all π-electron chromophore pair geometry choices that locally maximize the rate of conversion of a singlet exciton into singlet biexciton (triplet pair), using a simplified version of the diabatic frontier orbital model of singlet fission (SF). The resulting approximate optimal geometries provide insight and are expected to represent useful starting points for searches by more advanced methods. The general procedure is illustrated on a pair of ethylenes as the simplest model of a π-electron system, but it is applicable to pairs of much larger molecules, with dozens of non-hydrogen atoms, and not necessarily planar. We first examine the value of |TA|2, the square of the electronic matrix element for SF with initial excitation fully localized on partner A, on a grid of several billion geometries within the six-dimensional space of physically realizable possibilities. The optimized pair geometries are found to follow the qualitative guidance proposed earlier. In the neighborhood of each local maximum of |TA|2, consideration of mixing with charge-transfer configurations and of excitonic interaction between partners A and B determines the SF energy balance and yields squared matrix elements |T*|2 and |T**|2 for the lower and upper excitonic states S* and S**, respectively. Assuming Boltzmann populations of these states, the geometry is further optimized to maximize k, the sum of the SF rates obtained from Marcus theory, and this reorders the suitable geometries substantially. At 87 pair geometries, the |T*|2 and |T**|2 values are compared with those obtained from high-level ab initio non-orthogonal configuration interaction calculations and found to follow the same trend. Finally, the biexciton binding energy at the optimized geometries is calculated. Altogether 13 significant local maxima of SF rate for a pair of ethylenes are identified in the physically relevant part of space that avoids molecular interpenetration in the hard spheres approximation. The three best geometries are twist-stacked, slip-stacked, and L-shaped. The maxima occur at the (5-dimensional) surfaces of seven 6-dimensional “parent” regions of space centered at physically inaccessible geometries at which the calculated SF rate is very large but the two ethylenes interpenetrate. The results are displayed in interactive graphics. The computer code (“Simple”) written for these calculations is flexible in that it permits a choice of performing the search for local maxima in six dimensions on |TA|2, |T*|2, or k. It is available as freeware at https://cloud.uochb.cas.cz/simple.
Czech name
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Czech description
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Classification
Type
J<sub>imp</sub> - Article in a specialist periodical, which is included in the Web of Science database
CEP classification
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OECD FORD branch
10403 - Physical chemistry
Result continuities
Project
Result was created during the realization of more than one project. More information in the Projects tab.
Continuities
I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace
Others
Publication year
2019
Confidentiality
S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů
Data specific for result type
Name of the periodical
Journal of the American Chemical Society
ISSN
0002-7863
e-ISSN
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Volume of the periodical
141
Issue of the periodical within the volume
44
Country of publishing house
US - UNITED STATES
Number of pages
15
Pages from-to
17729-17743
UT code for WoS article
000495769300033
EID of the result in the Scopus database
2-s2.0-85074222916