First-principles study of phase transition of BaF2 under high pressue

doi:10.7498/aps.71.20211163

	First-principles study of phase transition of BaF2 under high pressue
	Tian Cheng 1,2; Lan Jian-Xiong 1,2; Wang Cang-Long 1,2; Zhai Peng-Fei 1,2; Liu Jie 1,2
刊名	ACTA PHYSICA SINICA
	2022-01-05
卷号	71 期号:1 页码:8
关键词	first-principles BaF2 phase transition hysteresis
ISSN号	1000-3290
DOI	10.7498/aps.71.20211163
通讯作者	Zhai Peng-Fei(zhaipengfei@impcas.ac.cn)
英文摘要	There have been some theoretical studies of high pressure phase transition behavior of BaF2, while in most cases the attention is paid mainly to the optical and electrical properties of BaF2 under increasing pressure. To date, there has been still a lack of theoretical explanation for the hysteresis phenomenon of high-pressure phase of BaF2 when the pressure is released. In addition, the pressure-dependent behavior of the BaF2 band gap is still under controversy, and there are few studies of its high-pressure Raman spectra. Therefore, first principle is used to make a supplementary calculation of the high pressure behavior of BaF2. For a given pressure P and temperature T, the thermodynamic stable phase has the lowest Gibbs free energy. The calculations are performed at zero temperature and hence, the Gibbs free energy becomes equal to the enthalpy. Thus, the variation of enthalpy is calculated as a function of pressure to study the high-pressure phase stability of BaF2 based on density functional theory as implemented in the Vienna ab initio simulation package (VASP). The results show that the BaF2 undergoes two structural phase transitions from Fm3m (cubic) to Pnma (orthorhombic) and then to P6(3)/mmc (hexagonal) with increasing pressure, and their corresponding transition pressures are 3.5 and 18.3 GPa, respectively. By calculating the evolution of lattice constant with pressure, it is found that at about 15 GPa (near the second phase transition pressure), the lattice constants of the Pnma structure show abnormal behavior (a slight increase in b(o) and a slight decrease in a(o)). We suggest that this behavior leads the band gap to decrease, indicated by analyzing the calculated results of Pnma structure of other materials. The Pnma structure completely transforms into P6(3)/mmc structure at about 20 GPa. By analyzing the phonon dispersion curves of BaF2 as a function of pressure, the structural stability information of the material can also be obtained. Then the density functional perturbation theory (DFPT) is used to calculate the phonon dispersion curves of BaF2 by VASP code and Phonopy code. The hysteresis phenomenon of the P6(3)/mmc structure, when the pressure is released, is explained by the kinetic stability. The results predict that the P6(3)/mmc structure can be stabilized at least to 80 GPa.
资助项目	National Natural Science Foundation of China[12075290] ; National Natural Science Foundation of China[12035019] ; Youth Innovation Promotion Association of Chinese Academy of Sciences[2020412] ; Opening Fund of Key Laboratory of Silicon Device and Technology, Chinese Academy of Sciences[KLSDTJJ2019-06]
WOS关键词	OPTICAL-PROPERTIES ; CAF2 ; SRF2 ; SUPERCONDUCTIVITY ; FLUORIDE
WOS研究方向	Physics
语种	英语
出版者	CHINESE PHYSICAL SOC
WOS记录号	WOS:000751859800028
资助机构	National Natural Science Foundation of China ; Youth Innovation Promotion Association of Chinese Academy of Sciences ; Opening Fund of Key Laboratory of Silicon Device and Technology, Chinese Academy of Sciences
内容类型	期刊论文
源URL	[http://119.78.100.186/handle/113462/142142]
专题	中国科学院近代物理研究所
通讯作者	Zhai Peng-Fei
作者单位	1.Chinese Acad Sci, Inst Modern Phys, Lanzhou 730000, Peoples R China 2.Univ Chinese Acad Sci, Sch Nucl Sci & Technol, Beijing 100049, Peoples R China
推荐引用方式 GB/T 7714	Tian Cheng,Lan Jian-Xiong,Wang Cang-Long,et al. First-principles study of phase transition of BaF2 under high pressue[J]. ACTA PHYSICA SINICA,2022,71(1):8.
APA	Tian Cheng,Lan Jian-Xiong,Wang Cang-Long,Zhai Peng-Fei,&Liu Jie.(2022).First-principles study of phase transition of BaF2 under high pressue.ACTA PHYSICA SINICA,71(1),8.
MLA	Tian Cheng,et al."First-principles study of phase transition of BaF2 under high pressue".ACTA PHYSICA SINICA 71.1(2022):8.