https://doi.org/10.1007/s100510050772
Theoretical description of adatom migration in two-dimensional highly-ordered states
1
Institute of Physics of the National Academy of Sciences, pr. Nauki 46, 252028, Kiev,
Ukraine
2
Max-Planck-Institut für Eisenforschung, 40074 Düsseldorf, Germany
3
Lehrstuhl für Physikalische Chemie II, Universität Dortmund, 44227 Dortmund,
Germany
Received:
24
June
1998
Published online: 15 May 1999
Analytical expressions for chemical, jump, and tracer diffusion
coefficients are obtained for interacting lattice gases on a square
lattice. Strongly repulsive nearest neighbor interactions cause the
formation of a highly-ordered c(2x2) state in the vicinity of
half coverage. It is shown that only strongly correlated successive
adatom jumps contribute to the particle flow. This allows to
describe the adatom kinetics by considering an almost ideal lattice
gas of defects. Two types of defects are considered, adatoms in the
empty sublattice and vacancies in the filled sublattice of the
c(2x2) ordered state. The diffusion equations for these defects
are developed considering the generation and recombination of defects.
In addition we have considered adatom transport caused by the motion of
defect pairs (dimers). Dimer transport mechanism prevails in the high
coverage region. The characteristic features of the various diffusion
coefficients near half coverage are analyzed and discussed. The theory
is compared with the results of sophisticated Monte-Carlo simulations
which have been executed with the use of a fully parallelized algorithm
on a Cray T3E (LC784-128). The agreement between theoretical and MC
results is excellent if the motion of dimers at is taken
into account.
PACS: 82.20.Mj – Nonequilibrium kinetics / 68.35.Fx – Diffusion; interface formation / 64.60.Cn – Order-disorder transformations; statistical mechanics of model systems
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 1999