It was shown that, at temperatures above 200K, X-irradiation in the presence of Li impurity stimulated the creation not only of the expected V4A centers, but also of V2 centers. With increasing impurity content and irradiation temperature (up to 300K), the creation of V2 centers, as stimulated by the impurities, increased by more than an order of magnitude; as compared with pure crystals. This was attributed to the ejection of small Li+ cations into interstitial sites, with the creation of cation vacancies. The onset temperature for mobility of the interstitial ions was estimated to be about 140K.

A.Z.Bekeshev, E.A.Vasilchenko, A.K.Dauletbekova, K.S.Shunkeev, A.A.Elango: Fizika Tverdogo Tela, 1996, 38[3], 769-78 (Physics of the Solid State, 1996, 38[3], 425-9)