Distortion-stabilized ordered structures in A_(2)BB’O_(7) mixed pyrochlores  

作　　者：Ghanshyam Pilania Brian Puchala Blas P.Uberuaga 

机构地区：[1]Materials Science and Technology Division,Los Alamos National Laboratory,Los Alamos,NM 87545,USA [2]Materials Science and Engineering Department,University of Michigan,Ann Arbor,MI 48109,USA

出　　处：《npj Computational Materials》2019年第1期1076-1084,共9页计算材料学（英文）

基　　金：The work was performed at the Los Alamos National Laboratory(LANL),an affirmative action equal opportunity employer,operated by Los Alamos National Security,LLC,for the National Nuclear Security Administration of the U.S.DOE under contract DE-AC52-06NA25396;Computational support for this work was provided by LANL’s high performance computing clusters.

摘　　要：Pyrochlore oxides(A2B2O7)are interesting for a number of technological applications,including radiation damage tolerance and as ionic conductors.Mixed pyrochlores—containing two A and/or two B site cations—provide even more flexibility for tailoring properties owing to the diverse chemical and configurational degrees of freedom accessible within this chemical space.Here,we examine relative stability of different cation orderings in one model double pyrochlore Gd2(Zr_(x)Ti_(1−x))_(2)O_(7),as a function of Zr content x.Our results show that,in the presence of some very specific local cation arrangements,certain cation-ordered compositions in this system are highly stabilized as a result of large oxygen relaxation displacements,leading to the formation of an ordered‘double’pyrochlore structure.The origins of these anomalous oxygen relaxations are traced back to both the local cation symmetry and a strong chemical preference of Zr atoms towards adopting a 7-fold coordination environment,as opposed to a 6-fold coordination available in a regular pyrochlore structure.Subsequently,we examine the stability of this type of ordering in 131 other pyrochlore compositions.Implications of our findings are discussed in relation to the observed composition-dependent ionic conductivity in these systems and connections with previously reported experimental findings are made.

关 键 词：structure ORDERED STABILIZED 

分 类 号：O61[理学—无机化学]