Publications (6)13.18 Total impact
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Article: Temperature for a dynamic spin ensemble.
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ABSTRACT: In molecular dynamics simulations, temperature is evaluated, via the equipartition principle, by computing the mean kinetic energy of atoms. There is no similar recipe yet for evaluating temperature of a dynamic system of interacting spins. By solving semiclassical Langevin spin-dynamics equations, and applying the fluctuation-dissipation theorem, we derive an equation for the temperature of a spin ensemble, expressed in terms of dynamic spin variables. The fact that definitions for the kinetic and spin temperatures are fully consistent is illustrated using large-scale spin dynamics and spin-lattice dynamics simulations.Physical Review E 09/2010; 82(3 Pt 1):031111. · 2.26 Impact Factor -
Article: Segregated void swelling in a spatially heterogeneous material
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ABSTRACT: We investigate the dynamics of void swelling in materials under irradiation in the presence of spatially heterogeneous dis-location microstructure. We find that, due to the sensitivity of the void nucleation rate to the local vacancy supersaturation, voids nucleate and grow almost exclusively in the regions where the density of dislocations is low. Numerical results show that the relatively high void growth rates observed experimentally in the regions of low dislocation density, leading to segregated evolution of dislocations and voids, can be naturally described by solutions of a reaction–diffusion model that takes continuous nucleation of voids into account but does not assume the occurrence of long-range one-dimensional transport of self-interstitial atoms through the material.Fusion Engineering and Design 01/2005; 7579:1031-1035. · 1.49 Impact Factor -
Article: Segregation of voids in a spatially heterogeneous dislocation microstructure
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ABSTRACT: We investigate the dynamics of nucleation and the growth of voids in an irradiated material in the presence of a spatially heterogeneous dislocation microstructure. We find that, due to the sensitivity of the void nucle-ation rate to the local vacancy supersaturation, voids nucleate and grow almost exclusively in the regions where the density of dislocations is low. Numerical simulations show that the relatively high void growth rates observed experimentally in the regions of low dislocation density, leading to segregated evolution of disloca-tions and voids, can be naturally described by solutions of a spatially heterogeneous reaction-diffusion model that takes continuous nucleation of voids into account but does not assume the occurrence of long-range one-dimensional transport of clusters of self-interstitial atoms through the material.Physical Review B 01/2004; 7082. · 3.69 Impact Factor -
Article: Heterogeneous void swelling near grain boundaries in irradiated materials
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ABSTRACT: We found that by assuming that the density of dislocations in an irradiated material varies as a function of the distance to grain boundaries and that mobile interstitial defect clusters perform three-dimensional diffu-sional motion it is possible to achieve significantly better agreement with experimental observations of profiles of heterogeneous void swelling than in the model where defects diffuse purely one-dimensionally. This ap-proach explains the origin of several distinct features characterising the effect of heterogeneous void swelling, including the variation of the shape of swelling profiles as a function of irradiation dose, the formation of peaks of swelling and void denuded zones, and the occurrence of anomalously large voids in the regions adjacent to grain boundaries.Physical Review B 01/2003; 67:094103. · 3.69 Impact Factor -
Article: Analysis of Microstructural Evolution Driven by Production Bias
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ABSTRACT: The concept of production Dras was first considered in the preceding workshop in this series at Silkeborg in 1989. Since then, much work has been done to investigate the validity of the concept, and its usefulness in complementing the current theory of microstructure evolution based solely on the sink bias (e.g., dislocation bias) as a driving force. Comparison of the theory with experimental results clearly supports the concept. The present paper reviews and summarizes these investiga-tions, and arrives at the following conclusions: a) the concept of production bias is consistent with the results of other works which indicates that, under cascade damage conditions, the effective rate of point-defect production is only a small fraction of the NRT displacement production rate; b) the defect accumulation under cascade damage conditions can be understood in terms of production bias; and c) although the existence of conventional dislocation bias due to point-defect dislocation interaction is not questioned, it does not seem to play any major role in the accumulation of defects under cascade damage conditions at elevated temperatures.Journal of Nuclear Materials 01/1993; 206:170-199. · 2.05 Impact Factor -
Article: Recent advances in the understanding of damage production and its consequences on void swelling, irradiation creep and growth
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ABSTRACT: The consequences of displacement damage produced by energetic particles on physical and mechanical properties of metals and alloys have been investigated both experimentally and theoretically for several decades. Over the years, a number of theoretical models have been proposed to rationalize the rate and magnitude of defect accumulation under different irradiation conditions. In recent years, significant advances have been made in understanding the nature of the damage produced in this form of multi-displacement cascades. The new knowledge regarding the intra-cascade recombination and clustering of self-interstitial atoms and vacancies during the cooling-down phase of cascades makes it necessary to re-examine the appropriateness of the available models for describing the accumulation of damage under cascade damage conditions. In this paper, recent advances in the understanding of damage production and its consequences are reviewed. A historic perspective is adopted. A comprehensive analysis of the effects of temperature, dose rate and particle type on multi-phenomena (swelling, creep, growth, microstructure evolution, RED, RIS) is presented to discuss the strength and weakness of various models, as they have evolved with the understanding of the damage processes. It has been shown that the irradiation damage modeling has progressed from the standard rate theory model to the BEK model to the production bias model with an increasing degree of sophistication as increasingly more realistic features of the irradiation damage production process were incorporated. It is shown that the newly proposed production bias model uniquely includes the necessary features of cascade damage production in its treatment of the damage accumulation.Journal of Nuclear Materials.
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Institutions
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2003–2010
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The Hong Kong Polytechnic University
- • Department of Electronic and Information Engineering
- • Department of Mechanical Engineering
Hong Kong, Hong Kong
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