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Estimates of the structure and dimerization energy of polyacetylene from ab initio calculations on finite polyenes
Author(s) -
Guo H.,
Paldus J.
Publication year - 1997
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/(sici)1097-461x(1997)63:2<345::aid-qua6>3.0.co;2-w
Subject(s) - polyacetylene , extrapolation , ab initio , bond energy , double bond , single bond , chemistry , sextuple bond , electronic correlation , bond order , triple bond , bond length , computational chemistry , bent bond , ab initio quantum chemistry methods , bond strength , molecule , mathematics , organic chemistry , group (periodic table) , mathematical analysis , adhesive , layer (electronics) , polymer
Abstract Ab initio calculations at the Hartree‐Fock (HF) and the second‐order Møller‐Plesset (MP2) levels are performed for finite polyenes C 2 n H 2 n +2 to estimate the structure and dimerization energy ( E dim ) of polyacetylene. The effect of electron correlation on the structure of finite polyenes is analyzed in detail. The MP3/6–31G* C(DOUBLE BOND)C and C(SINGLE BOND)C bond lengths in polyacetylene are estimated by a simple extrapolation method using empirical corrections for the MP2 deficiencies, yielding values [C(DOUBLE BOND)C(MP3) ∼ 1.36 Å and C(SINGLE BOND)C(MP3) ∼ 1.44 Å] that are in a good agreement with experiment (C(DOUBLE BOND)C (DOUBLE BOND) 1.36 Å and C(SINGLE BOND)C (DOUBLE BOND) 1.44–1.45 Å). Comparison is also made with other theoretical estimates of polyacetylene structure. E dim is approximated by the energy difference between the equilibrium and hypothetical polyenic structures. It is estimated that E dim is ∼ 1.4–1.5 kcal/mol (0.06–0.07 eV) per carbon‐carbon bond at the HF level with 4–21G and 6–31G* basis sets and ∼ 0.3–0.5 kcal/mol (0.013–0.022 eV) at the MP2 level with the 6–31G* basis set. It is concluded that E dim is very sensitive to the level of approximation employed so that a proper treatment of electron correlation is essential to obtain a reliable estimate of the dimerization energy. © 1997 John Wiley & Sons, Inc.