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Ab initio analysis of electron currents in thioalkanes
Author(s) -
Seminario Jorge M.,
Yan Liuming
Publication year - 2004
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/qua.20384
Subject(s) - homo/lumo , chemistry , atomic orbital , density functional theory , ab initio , molecular orbital , exponential function , alkane , electron , molecule , computational chemistry , molecular physics , atomic physics , chemical physics , physics , hydrocarbon , quantum mechanics , mathematical analysis , mathematics , organic chemistry
A combined density functional theory and Green's function procedure is used to calculate the electrical characteristics of a group of alkanethiols representing possible experimental settings. It is found that the current running through the molecule is the sum of the contributions from all molecular orbitals each presenting a barrier to electron transport equal to their energy difference from the Fermi level of the contacts. For the alkanethiols the location of these intrinsic barriers are at 0.78 eV (highest occupied molecular orbital [HOMO] and HOMO‐1), 1.99 eV (HOMO‐2 and HOMO‐3), 2.07 eV (LUMO and LUMO+1), and 2.67 eV (HOMO‐4). However, barriers obtained through fittings to known models do not bear any physical meaning at the molecular level, as they are sort of exponential average of the intrinsic barriers. We have also found that the exponential dependence of the current with the length of the alkane is practically independent of the contact nature, perhaps due to the large resistance of the alkanes. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005