COMPUTER MODELING AND BRILLOUIN-SCATTERING STUDIES OF ANHARMONICITY AND HIGH-TEMPERATURE DISORDER IN LAF3

被引:21
作者
NGOEPE, PE
JORDAN, WM
CATLOW, CRA
COMINS, JD
机构
[1] UNIV LONDON UNIV COLL,DEPT CHEM,LONDON WC1H 0AJ,ENGLAND
[2] UNIV KEELE,DEPT CHEM,KEELE ST5 5BG,STAFFS,ENGLAND
[3] UNIV WITWATERSRAND,DEPT PHYS,JOHANNESBURG 2050,SOUTH AFRICA
来源
PHYSICAL REVIEW B | 1990年 / 41卷 / 06期
关键词
D O I
10.1103/PhysRevB.41.3815
中图分类号
T [工业技术];
学科分类号
08 ;
摘要
Brillouin scattering studies of LaF3 at high temperatures have yielded the complete set of acoustic-mode frequencies associated with the elastic constants. These show a linear decrease with temperature up to about 1150 K, this being associated with lattice expansion. Above 1150 K, the elastic constants show a marked reduction with the exception of C44, which remains nearly constant. This behavior, which results from a diffuse superionic transition to a disordered state, has been computationally simulated by energy-minimization techniques. The nature of the dominant high-temperature disorder has been examined with the use of a supercell approach to permit appropriate defect concentrations and types. The calculations favor anion Frenkel disorder in an estimated concentration of 2 mole % at 1400 K. © 1990 The American Physical Society.
引用
收藏
页码:3815 / 3823
页数:9
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