Autowaves in Planar Molecular Structures
Y.B. Gaididei and V.Y. Chekh*
National Technical University of Ukraine
This is an abstract
for a poster to be presented at the
Fifth
Foresight Conference on Molecular Nanotechnology.
There will be a link from here to the full article when it is
available on the web.
The problem of investigations of charge density dynamics in
2-D molecular structures is actual for the development of future
molecular information processing devices. The model of the charge
transport has been investigated for the structures which consists
of such molecular chains: donor- mediator chain- acceptor
organized in Langmuir-Blodgett films on the substrate. It is
assumed that strong nonlinear charge carrier - conformation
interaction is presented for molecular donor and acceptor.
The initial Hamiltonian of the system's model has been reduced
to 3 nonlinear equations for homogenous systems (nonlinear
diffusion equations for heterogeneous ones) with the formalism of
density matrix. Their solutions were obtained by digital computer
modeling and phase space method.
It is shown that it is possible to initiate by optic pump some
dynamic effects of changing of charge density in the film with
presence of external electric field. Particularly, in homogenous
systems the following modes has been investigated:
- Bistable mode. The system tends to the
non-equilibrium phase transition from the monostable to
bistable modes at a well-defined pump level.
- Waiting mode. It is possible to discompose the
monostable system for relatively long period of time by
the momentary pump impulse.
- Relaxation oscillations are possible with the
stable pump and external voltage level as well as transition
to chaos accordingly to Feigenbaum scenario with the
periodically modulated optic pump level or [and] voltage.
In heterogeneous systems with well-defined parameters
the number of nonlinear waves (autowaves) and non-equilibrium
structures are possible to be initiated by the external optic
pump. Particularly, the following ones has been investigated:
- Stationary spatially heterogeneous structures are
possible in the systems where the diffusion coefficients
for charge carriers in the substrate are relatively
greater when in molecular film.
- Autowave processes "switch waves"
("trigger waves") are possible for the
heterogeneous systems with the parameters corresponds to
bistable mode of homogenous ones.
- Autowaves "traveling impulse" and
reverberators are possible to be initiated in the
systems which corresponds to waiting mode in homogenous
ones when the diffusion coefficients for the molecular
film are greater then for the substrate in the parallel
to the substrate (and film) plate direction.
All effects above could be demonstrated in a view of computer
animation. Stability of numerical solutions of the model
equations has been investigated as well.
*Corresponding Address:
Victor Yu. Chekh,16 Polytechnichna Str., Design Office
"Storm", National Technical University of Ukraine
252056 Kiev, Ukraine, ph: +038-044-274-0295, fax :
+038-044-274-1015, email : [email protected]
|