Aa. Stuchebrukhov, Ab initio calculations of long-distance electron tunneling in organometallic systems of biological origin, INT J QUANT, 77(1), 2000, pp. 16-26
The method of tunneling currents developed earlier by the author is applied
to study electron tunneling dynamics in a model organometallic donor-bridg
e-acceptor system in which the donor is the blue copper center in the reduc
ed form, the bridge is a polypeptide (5 glycine residues), and the acceptor
is -HisRu(III)(NH3)(5) complex. This system mimics pretty closely the majo
r amino-acid tunneling path in Ru-modified azurin studied by Gray and co-wo
rkers recently For the first time it is demonstrated that the tunneling mat
rix element as small as 10(-4) cm(-1) can be reliably evaluated using the a
b initio tunneling currents method. The method consists of an ab initio cal
culation of the spatial distribution of quantum mechanical flux of probabil
ity density occurring during the tunneling transition in the system, when a
n electron/hole tunnels from the donor site in the molecule to the acceptor
site. The analysis is based on the calculation of two diabatic nonorthogon
al electronic states corresponding to localization of a tunneling electron
on donor and acceptor sites, respectively, and subsequent evaluation of the
matrix element of current density operator between these two states. All e
lectrons in the system are taken into account at the Hartree-Fock level, an
d therefore the method allows one to examine the reaction of the background
electrons to the tunneling charge in a self-consistent way. Results for th
is system confirm earlier reported finding that in the tunneling flow there
exist quantized vortices, similar to those of a superfluid liquid, such as
Liquid He. (C) 2000 John Wiley & Sons, Inc.