Atomistic and Kinetic Simulations of Radiation Damage in Molybdenum
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Atomistic and Kinetic Simulations of Radiation Damage in Molybdenum
Zeke Insepov,1 Jeffrey Rest,1 Abdellatif M. Yacout,1 Bei Ye,1 Di Yun,1 Alexey Y Kuksin,2 Genri E Norman,2 Vladimir V Stegailov,2 Alexey V Yanilkin 2 1)
Argonne National Laboratory, Argonne, Illinois, USA
2)
Joint Institute for High Temperatures, Moscow, Russian Federation
ABSTRACT A new Mo potential, developed recently by using an ab initio quantum mechanics theory, was used to study formation and time evolution of radiation defects, such as self-interstitial atoms (SIAs), vacancies, and small clusters of SIAs, using molecular dynamics (MD). MD models were developed for calculation of the diffusion coefficients of vacancies, selfinterstitials, and small dislocation loops containing 2 to 37 SIAs; and the rate constants were calculated. Interactions of small SIA loops with SIAs were simulated. The results show that rotation of SIA from one to another equivalent direction is an important mechanism that significantly contributes to kinetic coefficients. INTRODUCTION Evolution of self-interstitial atoms (SIAs) and vacancies is the first stage of relaxation of a damaged structure after an intense ion bombardment and radiation cascade in metallic fuels. This stage plays an important role in the nucleation processes of dislocations and voids. The modern kinetic theory of radiation damage describes the kinetics of these processes in terms of the rate constants and interaction radius [1]. Recent MD results [2-8] demonstrated high mobility of dislocation loops composed of SIAs. The mobility of the dislocation loops was also observed experimentally in [9]. The description of loop in the kinetic rate theory is based on the sink strength of the dislocation loop [10], in which the loop growth and shrinkage are determined by the diffusion of point defects (SIA, vacancies). A recent ion bombardment experiment conducted on Mo thin films demonstrated a high escaping rate of the dislocation loops during the irradiation [11]. For the work presented here, a new embedded atom model (EAM)-interatomic potential of pure Mo was used that was recently developed using an Ab initio quantum mechanics theory [12]. The new potential was then used for static and dynamic atomistic simulations of the rates of binary reactions between the defects in Mo: of SIA with SIA and with vacancy. This potential was parameterized by a force-matching method (FMM), with a large set of configurations of defects and therefore was capable of reproducing a correct potential energy map and a hierarchy of the formation and migration energies of the defects. The calculations were carried out with the LAMMPS code [13].
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In this paper, the results of combination of this newly developed Mo interatomic potential with MD calculations of the diffusion coefficients of SIAs, vacancies, and dislocation loops containing 2 to 37 SIAs are presented, as well as the kinetic rate coefficients of dimer formation and defect recombination. The calculated data was supplied to a meso-scale kinetic rate theory model
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