Structure and Lattice Dynamics of MF2 (M = Ca, Sr, Ba, Pb) in Cubic and Orthorhombic Phases: The ab initio Calculations

Chernyshev, V. A.; Ryumshin, V. S.; Agzamova, P. A.

doi:10.1134/s1063783419010062

Cited by 1 publication

(6 citation statements)

References 34 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The presence of nine new peaks at 3.0(3) GPa indicated the transition to a cotunnite-type phase. The transition pressure from fluorite to the cotunnite structure determined in our study is consistent with previous results (3–3.2 GPa). , The observed nine peaks correspond to 4A g , B 1g , 3B 2g , and B 3g modes in the cotunnite structure . Softening of the A g mode at 15.5(4) GPa together with the presence of two new peaks indicates the transition to the Ni 2 In structure, consistent with literature results. , Two peaks above 15 GPa are E g modes in the Ni 2 In structure.…”

Section: Discussionsupporting

confidence: 92%

“… 5 , 36 The observed nine peaks correspond to 4A g , B 1g , 3B 2g , and B 3g modes in the cotunnite structure. 53 Softening of the A g mode at 15.5(4) GPa together with the presence of two new peaks indicates the transition to the Ni 2 In structure, consistent with literature results. 5 , 36 Two peaks above 15 GPa are E g modes in the Ni 2 In structure.…”

Section: Discussionsupporting

confidence: 90%

“…Black: rutile-type phase; pink: CaCl 2 -type phase; purple: PdF 2 -type phase; gray dashed lines: the calculated frequencies from Zhang et al 52 (b) CaF 2 . Blue: fluorite-type phase; green: cotunnite-type phase; gray open circles: the calculated frequencies from Chernyshev et al; 53 gray dashed lines: the experimental results from Speziale and Duffy. 34 (c) BaF 2 .…”

Section: Resultsmentioning

confidence: 99%

“… 34 (c) BaF 2 . Blue: fluorite-type phase; green: cotunnite-type phase; red: Ni 2 In-type phase; gray open circles: the calculated frequencies from Chernyshev et al 53 Solid circles: experimental data for samples with different orientations; solid lines: fitting results; gray dotted lines: the phase boundary of different phases.…”

Section: Resultsmentioning

confidence: 99%

“…5,34 According to recent computational results, there are 18 Raman-active modes (6A g , 3B 1g , 6B 2g , 3B 3g ) in the cotunnite-type phase (Figures 1 and 2). 53,74 The observed 13 peaks at 168−433(1) cm −1 at 9.6−39 GPa are related to 13 modes (5A g , 2B 1g , 4B 2g , 2B 3g ) among them. The peak at ∼265 cm −1 at 9.6(3) GPa, which exhibits downward dependence with pressure, is not the Raman-active mode of CaF 2 but is possibly due to the influence of fluorescence (Figures 1 and 2).…”

Section: Phase Transition Of Caf 2 At High P−tmentioning

confidence: 95%

See 4 more Smart Citations

High Pressure–Temperature Study of MgF₂, CaF₂, and BaF₂ by Raman Spectroscopy: Phase Transitions and Vibrational Properties of AF₂ Difluorides

Zhang,

Li,

et al. 2024

ACS Omega

View full text Add to dashboard Cite

The phase transition of AF2 difluorides strongly depends on pressure, temperature, and cationic radius. Here, we have investigated the phase transition of three difluorides, including MgF2, CaF2, and BaF2, at simultaneously high pressures and temperatures using Raman spectroscopy and X-ray diffraction in externally heated diamond anvil cells up to 55 GPa at 300–700 K. Rutile-type difluoride MgF2 with a small cationic radius undergoes a transition to the CaCl2-type phase at 9.9(1) GPa and 300 K, to the HP-PdF2-type phase at 21.0(2) GPa, and to the cotunnite-type phase at 44.2(2) GPa. The phase transition pressure to the HP-PdF2 and cotunnite structure at 300 K for our single crystal was found to be higher than that in previous studies using polycrystalline samples. Elevating the temperature increases the transition pressure from rutile- to the CaCl2-type phase but has a negative influence on the transition pressure when MgF2 transforms from the HP-PdF2- to cotunnite-type phase. Meanwhile, the transition pressure from the CaCl2- to HP-PdF2-type phase for MgF2 was identified to be independent of the temperature. Raman peaks suspected to belong to the α-PbO2-type phase were observed at 14.6–21.0(1) GPa and 400–700 K. At 300 K, difluorides CaF2 and BaF2 in the fluorite structure with larger cationic radii transform to the cotunnite-type phase at 9.6(3) and 3.0(3) GPa at 300 K, respectively, and BaF2 further undergoes a transition to the Ni2In-type phase at 15.5(4) GPa. For both CaF2 and BaF2, elevating the temperature leads to a lower transition pressure from fluorite- to the cotunnite-type phase but has little influence on the transition to the Ni2In structure. Raman data provide valuable insights for mode Grüneisen parameters. We note that the mode Grüneisen parameters for both difluorides and dioxides vary linearly with the cation radius. Further calculations for the mode Grüneisen parameters at high pressures for MgF2, CaF2, and BaF2 yield a deeper understanding of the thermodynamic properties of the difluorides.

show abstract

Section: Discussionsupporting

confidence: 92%

Section: Discussionsupporting

confidence: 90%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Phase Transition Of Caf 2 At High P−tmentioning

confidence: 95%

See 3 more Smart Citations

High Pressure–Temperature Study of MgF₂, CaF₂, and BaF₂ by Raman Spectroscopy: Phase Transitions and Vibrational Properties of AF₂ Difluorides

Zhang,

Li,

et al. 2024

ACS Omega

View full text Add to dashboard Cite

show abstract

Structure and Lattice Dynamics of MF2 (M = Ca, Sr, Ba, Pb) in Cubic and Orthorhombic Phases: The ab initio Calculations

Cited by 1 publication

References 34 publications

High Pressure–Temperature Study of MgF₂, CaF₂, and BaF₂ by Raman Spectroscopy: Phase Transitions and Vibrational Properties of AF₂ Difluorides

High Pressure–Temperature Study of MgF₂, CaF₂, and BaF₂ by Raman Spectroscopy: Phase Transitions and Vibrational Properties of AF₂ Difluorides

Contact Info

Product

Resources

About

Structure and Lattice Dynamics of MF2 (M = Ca, Sr, Ba, Pb) in Cubic and Orthorhombic Phases: The ab initio Calculations

Cited by 1 publication

References 34 publications

High Pressure–Temperature Study of MgF2, CaF2, and BaF2 by Raman Spectroscopy: Phase Transitions and Vibrational Properties of AF2 Difluorides

High Pressure–Temperature Study of MgF2, CaF2, and BaF2 by Raman Spectroscopy: Phase Transitions and Vibrational Properties of AF2 Difluorides

Contact Info

Product

Resources

About

High Pressure–Temperature Study of MgF₂, CaF₂, and BaF₂ by Raman Spectroscopy: Phase Transitions and Vibrational Properties of AF₂ Difluorides

High Pressure–Temperature Study of MgF₂, CaF₂, and BaF₂ by Raman Spectroscopy: Phase Transitions and Vibrational Properties of AF₂ Difluorides