Molecular dynamics modeling of radiation stability of Ca(Zr,Ti,Sn)O3 perovskitesтезисы доклада

Дата последнего поиска статьи во внешних источниках: 10 февраля 2016 г.

Работа с тезисами доклада

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1. Иллюстрация Radiation damage, produced by 20 keV Th recoil in Ca(Zr,Ti,Sn)O3 solid solution at the peak of the damage (left) and after structure relaxation (right). figure1.jpg 1,3 МБ 21 августа 2015 [neremin]

[1] Eremin N. N., Protasov N., Grechanovsky A. E. Molecular dynamics modeling of radiation stability of ca(zr,ti,sn)o3 perovskites // 29th European Crystallographic Meeting Book of Abstracts. — Rovinj, 2015. — P. 333–334. The main aim of this work was to investigate the relation between the radiation stability and the composition of Ca(Zr,Ti,Sn)O3 solid solution using method of molecular dynamics (MD). This compound with a rhombically distorted perovskite structure (space group Pbnm) is one of the promising matrices for utilization of high level radioactive waste. Note that a new mineral lakargiite, which represents the CaZrO3–CaTiO3–CaSnO3 solid solution with the maximal molar fraction x(CaZrO3) = 0.93 and maximal fractions x(CaTiO3) = 0.22 and x(CaSnO3) = 0.20, was registered in 2007 [1]. To simulate the solid solutions, it is necessary to solve the problem of atomic distribution in a computational supercell of limited size to imitate the disorder best and to determine the optimal dimension ality of such a supercell. Our original approach, described in [2] makes it possible to approach maximally the statistically disordered distribution in a macroscopic crystal in the framework of a cell of reasonable finite size. Thus, for MD simulation we used a nanofragment of the solid solution structure with different compositions with sizes 310×210×315 Å, which contains 1.4 million atoms with a maximally disordered distribution of Zr, Ti, and Sn. As an analog of the recoil atom the knocked out Th atom with energy of 20 keV was used. After the formation of the atomic displacement cascade at instant t=0.71 ps the structure starts to be “restored” and displaced atoms partially return to their sites or equivalent crystallographic sites. At the end of the simulation (t=20 ps), the total number of Frenkel pairs is minimal (figure 1). In contrast to some other tested materials where considerable amorphized regions remained at the end of simulation, these defects in CaZrO3–CaTiO3–CaSnO3 are mainly of the point character, which indicates the high stability of this solid solution to the radioactive effect. We evaluated parameter , which characterized susceptibility to amorphization of material under radiation damage. This parameter numerically equal to a part of the energy of Th atom, which is consumed for the formation of Frenkel pairs in a cascade of displaced atoms. It was shown that the dependence of -parameter on the solid solution composition is lowest for Sn-Zr compositions, whereas Ti-riched compositions exhibit poorer performance.We conclude with the following: the radiation stability of a mineral matrix with a chemical composition close to the lakargiite mineral is one of highest among the chemical compounds studied to date. Sn-Zr-riches matrices can be of unquestionable interest when solving both fundamental and applied problems associated with the isolation and burial of highly active radioactive wastes.

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