States of the Schottky defect in uranium dioxide and other fluorite type crystals: Molecular dynamics study / Kovalenko M. A.,Kupryazhkin A. Ya // JOURNAL OF ALLOYS AND COMPOUNDS. - 2015. - V. 645, l. . - P. 405-413.

ISSN/EISSN:

0925-8388 / 1873-4669

Type:

Article

Abstract:

Mass transfer processes in fluorite-type systems are determined by the diffusion of cations via vacancies from Schottky defects. To predict diffusion coefficients of cations and other parameters based on it the Lidiard and Matzke approximation of the point defects model, namely the assumption of isolated vacancies, is widely used. States of the Schottky defect were studied with the high-speed molecular dynamics method in a wide temperature range, with six different interaction potentials. Schottky vacancies were dynamically detected during the simulation. It is shown that contrary to the Lidiard and Matzke model, the Schottky cation vacancy is always associated with anion vacancies. The degree of the Schottky defect association depends on the temperature, at high temperatures near the cation vacancy two or more anion vacancies are located. It is shown that the calculated formation energy of Schottky defects in the form of the trivacancy (5.8-7.4) eV for all potentials are close to the experimental value (6-7) eV, in contrast to the formation energy of Schottky defects in the form of isolated vacancies that exceeds 10 eV. Point defects model of the simulated system in the presence of an artificially created Schottky defect was constructed and compared with calculation results. According to our study the point defects model is applicable only at low temperatures less than half of the melting temperature. It is shown that the presence of anion vacancies near the cation vacancy reduces the migration energy of cations. However, for systems with several Schottky defects the vacancy clusterization and the formation of voids are observed. This leads to an increase of the diffusion activation energy due to the contribution of the energy that needs to separate the single cation vacancy from the void. (C) 2015 Elsevier B.V. All rights reserved.

Author keywords:

Molecular dynamics simulations; Schottky defect; Diffusion; Point defects model; Uranium dioxide; Vacancy migration SELF-DIFFUSION; INTERATOMIC POTENTIALS; MASS-TRANSPORT; UO2; TEMPERATURES; SIMULATIONS; MECHANISMS; POINT; CAF2

DOI:

10.1016/j.jallcom.2015.05.111

Web of Science ID:

ISI:000357146300059

Соавторы в МНС:

Другие поля

Поле	Значение
Month	OCT 5
Publisher	ELSEVIER SCIENCE SA
Address	PO BOX 564, 1001 LAUSANNE, SWITZERLAND
Language	English
EISSN	1873-4669
Keywords-Plus	SELF-DIFFUSION; INTERATOMIC POTENTIALS; MASS-TRANSPORT; UO2; TEMPERATURES; SIMULATIONS; MECHANISMS; POINT; CAF2
Research-Areas	Chemistry; Materials Science; Metallurgy \& Metallurgical Engineering
Web-of-Science-Categories	Chemistry, Physical; Materials Science, Multidisciplinary; Metallurgy \& Metallurgical Engineering
Author-Email	akm\_max@mail.ru a.ya.kupryazhkin@urfu.ru
Funding-Acknowledgement	UrFU
Funding-Text	This research project has been supported by UrFU under the Framework Programme of development of UrFU through the Young scientists UrFU competition.
Number-of-Cited-References	28
Usage-Count-Last-180-days	5
Usage-Count-Since-2013	46
Journal-ISO	J. Alloy. Compd.
Doc-Delivery-Number	CL7IS