Dynamics of antipolar distortions

作     者：Kinnary Patel Sergey Prosandeev Laurent Bellaiche 

作者机构：Physics Department and Institute for Nanoscience and EngineeringUniversity of ArkansasFayettevilleAR 72701USA Institute of Physics and Physics Department of Southern Federal UniversityRostov-na-Donu 344090Russia 

出 版 物：《npj Computational Materials》 (计算材料学（英文）)

年 卷 期：2017年第3卷第1期

页      面：171-178页

核心收录：

学科分类：081704[工学-应用化学] 07[理学] 08[工学] 0817[工学-化学工程与技术] 070303[理学-有机化学] 0703[理学-化学] 

基　　金：ARO Grant No.W911NF-16-1-0227 the support of Air Force Office of Scientific Research under Grant No.FA9550-16-1-0065 the grants 3.1649.2017/4.6 from RMES(Russian Ministry of Education and Science) 16-52-0072_Bel_a from RFBR(Russian Foundation for Basic Research) 

主　　题：polar distortion phonon 

摘      要：Materials possessing antipolar cation motions are currently receiving a lot of attention because they are fundamentally intriguing while being technologically *** studies devoted to these complex materials have focused on their static properties or on their zone-center *** a result,some important dynamics of antipolar cation distortions,such as the temperature behavior of their phonon frequencies,have been much less investigated,despite the possibility to exhibit unusual ***,we report the results and analysis of atomistic simulations revealing and explaining such dynamics for BiFeO3 bulks being subject to hydrostatic *** is first predicted that cooling such material yields the following phase transition sequence:the cubic paraelectric Pm3m state at high temperature,followed by an intermediate phase possessing long-range-ordered in-phase oxygen octahedral tiltings,and then the Pnma state that is known to possess antipolar cation motions in addition to in-phase and antiphase oxygen octahedral *** cation modes are found to all have high phonon frequencies that are independent of temperature in the paraelectric *** the other hand and in addition to antipolar cation modes increasing in number,some phonons possessing antipolar cation character are rather soft in the intermediate and Pnma *** of our data combined with the development of a simple model reveals that such features originate from a dynamical mixing between pure antipolar cation phonons and fluctuations of oxygen octahedral tiltings,as a result of a specific trilinear energetic *** developed model can also be easily applied to predict dynamics of antipolar cation motions for other possible structural paths bringing Pm3m to Pnma states.