Improved Statistical Exchange Approximation for Inhomogeneous Many-Electron Systems

1969 ◽  
Vol 22 (16) ◽  
pp. 807-811 ◽  
Author(s):  
Frank Herman ◽  
John P. Van Dyke ◽  
Irene B. Ortenburger
Keyword(s):  
Electron Systems ◽  
Exchange Approximation ◽  
Statistical Exchange

Studies of the Statistical Exchange Approximation in First-Transition-Row Atoms and Ions:Mn+2Ion

1970 ◽  
Vol 2 (3) ◽  
pp. 620-634 ◽  
Author(s):  
Timothy M. Wilson ◽  
J. H. Wood ◽  
J. C. Slater
Keyword(s):  
Exchange Approximation ◽  
Statistical Exchange

Notizen: Orbital Binding Energies within the Statistical Exchange Approximation: Ne and Ar Isoelectronic Series

1979 ◽  
Vol 34 (7) ◽  
pp. 901-902 ◽  
Author(s):  
K. D. Sen
Keyword(s):  
Binding Energies ◽  
Hartree Fock ◽  
Orbital Energies ◽  
Isoelectronic Series ◽  
Exchange Approximation ◽  
Statistical Exchange ◽  
Good Agreement

Binding energies are calculated using the orbital energies within the Kohn-Sham-Gaspar statistical exchange approx­imation for the Xe and Ar isoelectronic series, respectively. The results are generally in good agreement with the available Hartree-Fock orbital energies.

Pathway Complexity in the Stacking of Imine-linked Macrocycles Related to Two-Dimensional Covalent Organic Frameworks

2019 ◽  
Author(s):  
Shiwei Wang ◽  
Anton Chavez ◽  
Simil Thomas ◽  
Hong Li ◽  
Nathan C. Flanders ◽  
...  
Keyword(s):  
Temperature Dependence ◽  
Structural Similarity ◽  
Discrete Models ◽  
Side Chains ◽  
Two Dimensional ◽  
Assembly Process ◽  
Covalent Organic Frameworks ◽  
Electron Systems ◽  
Monomer Structure ◽  
Kinetic Traps

This work reports on the assembly of imine-linked macrocycles that serve as models of two-dimensional covalent organic frameworks (2D COFs). Interlayer interactions play an important role in the formation of 2D COFs, yet the effect of monomer structure on COF formation, crystallinity, and susceptibility to exfoliation are not well understood. For example, monomers with both electron-rich and electron-poor π-electron systems have been proposed to strengthen interlayer inter-actions and improve crystallinity. Here we probe these effects by studying the stacking behavior of imine-linked macrocycles that represent discrete models of 2D COFs. <div><br></div><div>Specifically, macrocycles based on terephthaldehyde (PDA) or 2,5-dimethoxyterephthaldehyde (DMPDA) stack upon cooling molecularly dissolved solutions. Both macrocycles assemble cooperatively with similar ΔHe values of -97 kJ/mol and -101 kJ/mol, respectively, although the DMPDA macrocycle assembly process showed a more straightforward temperature dependence. Circular dichroism spectroscopy performed on macrocycles bearing chiral side chains revealed a helix reversion process for the PDA macrocycles that was not observed for the DMPDA macrocycles. <br></div><div><br></div><div>Given the structural similarity of these monomers, these findings demonstrate that the stacking processes associated with nanotubes derived from these macrocycles, as well as for the corresponding COFs, are complex and susceptible to kinetic traps, casting doubt on the relevance of thermodynamic arguments for improving materials quality. <br></div>

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