Structure, thermodynamics, and electronic properties are predicted for a new low energy phase of carbon which contains planar sheets equally occupied by sp2 and sp carbon atoms. The isolated planar sheets have the same planar symmetry as do the layers in graphite (p6m) and can be formally viewed as resulting from the replacement of one‐third of the carbon–carbon bonds in graphite by –C 3/4 C– linkages. This material, called graphyne, is predicted to have a crystalline state formation energy of 12.4 kcal/mol carbon, which appears to be much lower than for any carbon phase which contains acetylenic groups as a major structural component. Based on the major structural reorganization required for graphitization and the observed high temperature stability of known model compounds, high temperature stability is predicted for graphyne. While graphyne will have similar mechanical properties as graphite, it is predicted to be a large bandgap semiconductor (Eg=1.2 eV) rather than a metal or semimetal. Based on this...

Structure‐property predictions for new planar forms of carbon: Layered phases containing sp2 and sp atoms

The understanding of the dual fluorescence of certain aromatic systems has greatly advanced in recent years. The accompanying large charge separation has been shown to be linked to a twisted (or small overlap) arrangement of the chromophores. Recent theoretical models are able to describe the excited-state twisting of both single bonds (TICT compounds) and double bonds (olefins) in a unified picture. These models can help to elucidate the photophysical behavior of many organic, inorganic, and biologically relevant compounds, and their application to laser dyes and fluorescent probes provides a route to new “tailor-made” fluorescent materials. Applied to the primary processes of vision and photosynthesis, these models can lead to a deeper understanding of basic photobiological processes.

Charge Separation in Excited States of Decoupled Systems—TICT Compounds and Implications Regarding the Development of New Laser Dyes and the Primary Process of Vision and Photosynthesis

Anisotropy of the Induced Current Density (ACID), a General Method To Quantify and Visualize Electronic Delocalization

Computations of activation barriers and reaction energies for 1,3-dipolar cycloadditions by a high-accuracy quantum mechanical method (CBS-QB3) now reveal previously unrecognized quantitative trends in activation barriers. The distortion/interaction theory explains why (1) there is a monotonic decrease of ∼6 kcal/mol in the barrier height along the series oxides, imine, and ylide, for each class of 1,3-dipoles; (2) the corresponding nitrilium and azomethine betaines have almost identical cycloaddition barrier heights; (3) cycloadditions of a given 1,3-dipole with ethylene and acetylene have the same activation energies, in spite of very different reaction thermodynamics and frontier orbital gaps. There is a linear correlation between distortion energies (ΔEd⧧) and the activation barrier (ΔE⧧ = 0.75ΔEd⧧ − 2.9 kcal/mol) that is general for substituted and unsubstituted 1,3-dipoles in these cycloadditions. The energy to distort the 1,3-dipole to the geometry favorable for interaction with the dipolarophile, ...

Distortion/Interaction Energy Control of 1,3-Dipolar Cycloaddition Reactivity

During the establishment phase of a biological invasion, population dynamics are strongly influenced by Allee effects and stochastic dynamics, both of which may lead to extinction of low-density populations. Allee effects refer to a decline in population growth rate with a decline in abundance and can arise from various mechanisms. Strategies to eradicate newly established populations should focus on either enhancing Allee effects or suppressing populations below Allee thresholds, such that extinction proceeds without further intervention. The spread phase of invasions results from the coupling of population growth with dispersal. Reaction-diffusion is the simplest form of spread, resulting in continuous expansion and asymptotically constant radial rates of spread. However, spread of most nonindigenous insects is characterized by occasional long-distance dispersal, which results in the formation of isolated colonies that grow, coalesce, and greatly increase spread. Allee effects also affect spread, generally in a negative fashion. Efforts to slow, stop, or reverse spread should incorporate the spread dynamics unique to the target species.

https://www.nrs.fs.fed.us/pubs/jrnl/2008/nrs_2008_liebhold_001.pdf

Population ecology of insect invasions and their management

Barriers to thermally allowed reactions and the elusiveness of neutral homoaromaticity

Theoretical studies of the structures and reactions of substituted carbonyl ylides

The physical model for the self-diffusion of a gaseous material is applied to the analysis of insect dispersal data. Because this model is derived from well-understood mathematical principles, the model provides biological information not available from other models. In particular, through application of the model in analyzing dispersal data, one can obtain an independent estimate of mortality in the field. The model also provides some behavioral data. Examples of the application of the model to data sets from the literature are given.

Diffusion Model for Insect Dispersal

A sudden-polarization model to predict regioselectivities and periselectivities of the 1,7-sigmatropic shifts and electrocyclizations of singlet excited states of cycloheptatrienes

Ruth Wells Gandour

Papers

Barriers to thermally allowed reactions and the elusiveness of neutral homoaromaticity

Theoretical studies of the structures and reactions of substituted carbonyl ylides

Diffusion Model for Insect Dispersal

A sudden-polarization model to predict regioselectivities and periselectivities of the 1,7-sigmatropic shifts and electrocyclizations of singlet excited states of cycloheptatrienes

Electronic structure and photoelectron spectrum of 1,5,9-cyclododecatriyne