Measures of unpaired electrons for large conjugated systems

Autor:	A. V. Luzanov
Rok vydání:	2014
Předmět:	Inorganic Chemistry Coupled cluster Character (mathematics) Electronic correlation Unpaired electron Solid-state physics Chemistry Quantum mechanics Materials Chemistry Physical and Theoretical Chemistry Configuration interaction Representation (mathematics) Measure (mathematics)
Zdroj:	Journal of Structural Chemistry. 55:799-808
ISSN:	1573-8779 0022-4766
DOI:	10.1134/s0022476614050011
Popis:	It is shown that the numerical measure of effectively unpaired electrons Neff, proposed by Head-Gordon in 2003, is a particle-hole index: Neff is reduced to the average occupation of virtual particle-hole pairs. Specific π calculations of the Neff index provide a reasonable interpretation of the radicaloid character of the singlet ground state in complex conjugated systems. The results of the accurate π model (based on the total configuration interaction) and approximate approaches are compared. The coupled cluster method and various Hartree-Fock schemes (UHF and Lowdin EHF scheme) demonstrate an acceptable quantitative description of unpairing effects, UHF being favorable in simplicity of obtaining the measure of unpairing in megamolecules, such as graphene structures. The application of the known Yamaguchi index results in a rougher representation of the radical character of a system.
Databáze:	OpenAIRE
Externí odkaz:	https://explore.openaire.eu/search/publication?articleId=doi_________::cee9db7f624649bc4c5084e64eab8f4a https://doi.org/10.1134/s0022476614050011 Zobrazit plný text záznamu Plný text ve formátu PDF