Elastic and electronic properties and stability of SrThO 3 , SrZrO 3 and ThO 2 from first principles I.R. Shein, K.I. Shein, A.L. Ivanovskii * Institute of Solid State Chemistry, Ural Branch of the Russian Academy of Sciences, 620041 Ekaterinburg, Russia Received 13 September 2006; accepted 17 November 2006 Abstract First-principle calculations in the framework of the full-potential linearized-augmented-plane-wave method (FLAPW, as implemented into the WIEN-2k code) have been performed to understand the structural, elastic, cohesive and electronic properties of the meta-stable cubic strontium thorate SrThO 3 . The optimized lattice parameters, elastic parameters, formation energies, densities of states, band structures and charge density distributions are obtained and discussed in comparison with those of cubic SrZrO 3 and ThO 2 . Ó 2006 Elsevier B.V. All rights reserved. 1. Introduction Thorium-based nuclear fuels are of great interest for the future nuclear industry. For example, it is proposed to use a ThO 2 matrix with admixtures of uranium and plutonium oxides as advanced fuel materials for the thermal breeder reactors and high-temperature gas cooled reactors. In this con- text, the presence of low-density phases such as ternary oxides M 2 ThO 3 or MThO 3 forming due to the interaction of the fission products (M = Rb, Ba, Sr, etc.) with thoria, may critically affect the properties of the fuel such as thermal expansion, conductivity, and can be also responsible for the swelling of the fuel pins, see [1–3]. Since strontium is among the predominant fission products, the properties of the perovskite-like stron- tium thorate (SrThO 3 ) caused a lot of interest during the last decade [1–5]. Furthermore, the perovskite-type multi-component oxides of actini- des are interesting candidates for hydrogen sensors, hydrogen gas separators, and are useful materials for many other electrochemical applications because of the unusual combination of their electronic and transport properties [6]. For the first time the synthesis of SrThO 3 by a conventional solid state route was reported in 1947 by Mary-Szabo [7]. More recently, Subasri et al. [5] noted the very limited solubility of SrO in thoria, and the formation of the single ternary phase is not achieved. On other hand, SrThO 3 samples are successfully prepared by a sol–gel method through the gel combustion technique [2–4]. The stability of SrThO 3 phase was discussed [3,4], using experimentally derived and calculated 0022-3115/$ - see front matter Ó 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jnucmat.2006.11.003 * Corresponding author. Tel.: +7 343 3755331; fax: +7 373 3744495. E-mail address: ivanovskii@ihim.uran.ru (A.L. Ivanovskii). Journal of Nuclear Materials 361 (2007) 69–77 www.elsevier.com/locate/jnucmat