82 research outputs found
Theory of a quodon gas. With application to precipitation kinetics in solids under irradiation
Rate theory of the radiation-induced precipitation in solids is modified with
account of non-equilibrium fluctuations driven by the gas of lattice solitons
(a.k.a. quodons) produced by irradiation. According to quantitative
estimations, a steady-state density of the quodon gas under sufficiently
intense irradiation can be as high as the density of phonon gas. The quodon gas
may be a powerful driver of the chemical reaction rates under irradiation, the
strength of which exponentially increases with irradiation flux and may be
comparable with strength of the phonon gas that exponentially increases with
temperature. The modified rate theory is applied to modelling of copper
precipitation in FeCu binary alloys under electron irradiation. In contrast to
the classical rate theory, which disagrees strongly with experimental data on
all precipitation parameters, the modified rate theory describes quite well
both the evolution of precipitates and the matrix concentration of copper
measured by different methodsComment: V. Dubinko, R. Shapovalov, Theory of a quodon gas. With application
to precipitation kinetics in solids under irradiation. (Springer
International Publishing, Switzerland, 2014
Reaction rate theory with account of the crystal anharmonicity
Reaction rate theory in solids is modified taking into account intrinsic
localized modes or discrete breathers (DBs) that can appear in crystals with
sufficient anharmonicity resulting in violation of Arrhenius law. Large
amplitude oscillations of atoms about their equilibrium positions in the
lattice cause local potentials of alternating sign, which are described in
terms of time-periodic modulations of the potential barriers for chemical
reactions taking place in the vicinity of DBs. The reaction rate averaged over
large macroscopic volumes and times including a lot of DBs is increased by a
factor that depends on the DB statistics. The breather statistics in thermal
equilibrium and in thermal spikes in solids under irradiation with swift
particles is considered, and the corresponding reaction rate amplification
factors are derived.Comment: 17 pages, 12 figure
Quantum dynamics of wave packets in a non-stationary parabolic potential and the Kramers escape rate theory
At sufficiently low temperatures, the reaction rates in solids are controlled by quantum rather than by thermal fluctuations. We solve the Schrödinger equation for a Gaussian wave packet in a non-stationary harmonic oscillator and derive simple analytical expressions for the increase of its mean energy with time induced by the time-periodic modulation. Applying these expressions to the modified Kramers theory, we demonstrate a strong increase of the rate of escape out of a potential well under the time-periodic driving, when the driving frequency of the well position equals its eigenfrequency, or when the driving frequency of the well width exceeds its eigenfrequency by a factor of ~2~2. Such regimes can be realized near localized anharmonic vibrations (LAVs), in which the amplitude of atomic oscillations greatly exceeds that of harmonic oscillations (phonons) that determine the system temperature. LAVs can be excited either thermally or by external triggering, which can result in strong catalytic effects due to amplification of the Kramers rate
Rate theory of acceleration of the defect annealing driven by discrete breathers
Novel mechanisms of defect annealing in solids are discussed, which are based
on the large amplitude anharmonic lattice vibrations, a.k.a. intrinsic
localized modes or discrete breathers (DBs). A model for amplification of
defect annealing rate in Ge by low energy plasma-generated DBs is proposed, in
which, based on recent atomistic modelling, it is assumed that DBs can excite
atoms around defects rather strongly, giving them energy for
100 oscillation periods. This is shown to result in the amplification of
the annealing rates proportional to the DB flux, i.e. to the flux of ions (or
energetic atoms) impinging at the Ge surface from inductively coupled plasma
(ICP)Comment: 18 pages, 11 figures. arXiv admin note: text overlap with
arXiv:1406.394
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