Pressure-induced ferroelectric and anti-ferroelectric phase transitions in LaN

作     者：Chi Ding Jianan Yuan Beatriz H.Cogollo-Olivo Yunlong Wang Xiaomeng Wang Jian Sun 

作者机构：National Laboratory of Solid State MicrostructuresSchool of Physics and Collaborative Innovation Center of Advanced MicrostructuresNanjingUniversityNanjing 210093China Applied Math InstituteUniversity of CartagenaCartagena de Indias 130001Colombia 

出 版 物：《Science China(Physics,Mechanics & Astronomy)》 (中国科学：物理学、力学、天文学（英文版）)

年 卷 期：2023年第66卷第2期

页      面：122-130页

核心收录：

学科分类：08[工学] 0805[工学-材料科学与工程（可授工学、理学学位）] 0703[理学-化学] 

基　　金：supported by the National Natural Science Foundation of China (Grant Nos. 12125404, 11974162, and 11834006) the Fundamental Research Funds for the Central Universities。 

主　　题：ferroelectric phase distortion 

摘      要：In this work,we focus on the structural and electronic properties of lanthanum mono-nitride s under high pressure.Based on firstprinciples calculations and crystal structure predictions,we identified an anti-ferroelectric orthogonal phase with space group Pbcm.It is predicted to be thermodynamically stable from 20 to 60 GPa,above which the tetragonal phase without the antiferroelectric distortion will substitute it.However,the anti-ferroelectric distortion can be enhancedby reducing the pressure,and a phase transition to a NiAs-type(B8,P63/mmc) structure occurs at about 20 GPa.The calculated double-well potential for La atoms along the c direction in the B8 phase reveals that it should exhibit ferroelectric properties at low temperatures.Enthalpy calculations well confirm their phase transition sequences under high pressure.Electtonic properties calculations suggest that all the newly identified phases are semiconductors and the corresponding structural distortions can increase their bandgaps.When increasing the pressure to 50 GPa,the tetragonal phase undergoes a semiconductor-to-semimetal transition.Taking the spin-orbit coupling into account,the semimetal phase becomes a topological insulator with a small bandgap.Finally,given the similarities between the ionic compounds LaN and BaO,we predict that the most stable phase for BaO at about 25 GPa should also be the anti-ferroelectric orthogonal phase instead of the tetragonal phase.