Nanoscale patterning of chemical order induced by displacement cascades in irradiated L1{sub 0} alloys: Scaling analysis of the fluctuations of order
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana-Champaign, Illinois 61801 (United States)
Atomistic kinetic Monte Carlo simulations are employed to analyze the dynamical stabilization of nanoscale patterning of L1{sub 0} chemical order in a model binary alloy subjected to sustained irradiation. The effect of irradiation-induced displacement cascades on the chemical order is modeled by the introduction at a controlled rate of nearly fully disordered spherical zones, which compete with the reordering promoted by the thermally activated migration of vacancies. When the size of the disordered zones is small, the alloy reaches a steady state that is either long-range ordered at low irradiation-induced ballistic jump frequency, {gamma}{sub b}, or disordered at high {gamma}{sub b}, with a first-order dynamical transition between these two steady states at {gamma}{sub b}={gamma}{sub b}{sup c}. Furthermore, in the disordered steady state, the intensity of order fluctuations scales with the reduced variable {gamma}{sub b}/{gamma}{sub b}{sup c}, a scaling that is consistent with an effective temperature approach. For larger cascade sizes, however, an additional steady state is stabilized at intermediate ballistic jump frequency, with a microstructure comprised of well-ordered nanoscale domains. In this patterning-of-order steady state, the above rescaling breaks down but we show that, after deconvolution of the structure factor into Gaussian and Lorentzian components, scaling of the Gaussian component is recovered by introducing a new reduced variable, {gamma}{sub b}/{gamma}{sub b}{sup p}, where 1/{gamma}{sub b}{sup p} is interpreted as the characteristic time for new domains to form in a disordered zone. This new scaling relationship provides a rigorous definition of the regime of patterning of order. This regime corresponds to the steady states stabilized by cascade sizes and ballistic jump frequencies satisfying {gamma}{sub b}{sup c}{<=}{gamma}{sub b}{<=}{gamma}{sub b}{sup p}. A dynamical phase diagram based on this new criterion is constructed and it agrees well with direct visualization of atomic configurations. Extensions to nonstoichiometric compositions are investigated. Consequences for the direct synthesis of functional nanocomposite structures comprised of chemically ordered phases are discussed.
- OSTI ID:
- 20853247
- Journal Information:
- Physical Review. B, Condensed Matter and Materials Physics, Vol. 73, Issue 22; Other Information: DOI: 10.1103/PhysRevB.73.224121; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1098-0121
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
SUPERCONDUCTIVITY AND SUPERFLUIDITY
36 MATERIALS SCIENCE
BINARY ALLOY SYSTEMS
COMPUTERIZED SIMULATION
CRYSTALS
FLUCTUATIONS
IRRADIATION
LITHIUM ALLOYS
MICROSTRUCTURE
MONTE CARLO METHOD
NANOSTRUCTURES
PHASE DIAGRAMS
PHYSICAL RADIATION EFFECTS
SPHERICAL CONFIGURATION
STABILIZATION
STOICHIOMETRY
STRUCTURE FACTORS
SYNTHESIS
VACANCIES
ZONES