High-pressure structural phase transitions and intermediate phases of magnesium fluoride

Öztürk, Hülya; Kürkçü, Cemile; Kürkçü, Cihan

doi:10.1016/j.jallcom.2014.01.221

Cited by 17 publications

(9 citation statements)

References 32 publications

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“…22 Similarly, ab initio molecular dynamic studies have been performed on ZrO 2 23 and MgF 2 constructs. 24 In an experimental study, transitions from rutile to CaCl 2 phase have been observed by Prakapenka and co-workers 1 and in this experimental study lattice constants for rutile were found as a= 4.407 Å, c=2.862 Å and lattice constants for 3 and similarly, bulk modulus B 0 = 250 GPa and B 0 = 262 GPa.…”

supporting

confidence: 64%

“…22 Similarly, ab initio molecular dynamic studies have been performed on ZrO 2 23 and MgF 2 constructs. 24 In an experimental study, transitions from rutile to CaCl 2 phase have been observed by Prakapenka and co-workers 1 and in this experimental study lattice constants for rutile were found as a= 4.407 Å, c=2.862 Å and lattice constants for In this study, we found these values for the rutile phase as a = 4.420 Å, c = 2.914 Å and B 0 = 269 GPa; and for CaCl 2 phase as a = 4.375 Å and B 0 = 259 GPa. In Table 2, our results were compared with other studies.…”

mentioning

confidence: 99%

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Phase transition of GeO2 crystal at high pressure: An ab initio molecular dynamics study

Alptekin

2020

International Journal of Chemistry and Technology

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The phase transition of GeO 2 structure was studied under constant pressure by using ab initio calculation and the generalized gradient approximation (GGA). A structural phase transition was observed at 30 GPa for the first time under the constant hydrostatic pressure, and P4 2 /mnm structure was transformated into a CaCl 2 (Pnnm) structure. This phase transition was also investigated using total energy, enthalpy, and the phase shift calculations. It was determined that the obtained transformation parameters and bulk modulus properties were compatible with the previous experimental and theoretical first principle calculations.

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supporting

confidence: 64%

“…22 Similarly, ab initio molecular dynamic studies have been performed on ZrO 2 23 and MgF 2 constructs. 24 In an experimental study, transitions from rutile to CaCl 2 phase have been observed by Prakapenka and co-workers 1 and in this experimental study lattice constants for rutile were found as a= 4.407 Å, c=2.862 Å and lattice constants for In this study, we found these values for the rutile phase as a = 4.420 Å, c = 2.914 Å and B 0 = 269 GPa; and for CaCl 2 phase as a = 4.375 Å and B 0 = 259 GPa. In Table 2, our results were compared with other studies.…”

mentioning

confidence: 99%

Phase transition of GeO2 crystal at high pressure: An ab initio molecular dynamics study

Alptekin

2020

International Journal of Chemistry and Technology

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“…The He atoms are inserted into the octahedral sites, thus also forming an FCC lattice. The A 2 B compounds also share similar structures at low pressure: Li 2 O and CaF 2 adopt the same CaF 2 -type structure at ambient pressure, and MgF 2 takes up the TiO 2 structure 50 , 51 . However, these structures have large interstices, making for an inefficient packing, and they will not be thermodynamically favored under very high pressure.…”

Section: Resultsmentioning

confidence: 95%

Reactivity of He with ionic compounds under high pressure

et al. 2018

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Until very recently, helium had remained the last naturally occurring element that was known not to form stable solid compounds. Here we propose and demonstrate that there is a general driving force for helium to react with ionic compounds that contain an unequal number of cations and anions. The corresponding reaction products are stabilized not by local chemical bonds but by long-range Coulomb interactions that are significantly modified by the insertion of helium atoms, especially under high pressure. This mechanism also explains the recently discovered reactivity of He and Na under pressure. Our work reveals that helium has the propensity to react with a broad range of ionic compounds at pressures as low as 30 GPa. Since most of the Earth’s minerals contain unequal numbers of positively and negatively charged atoms, our work suggests that large quantities of He might be stored in the Earth’s lower mantle.

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“…The results from our structure searches are given in Previous theoretical studies [43,44] have already considered the rutile, α-PbO 2 , pyrite and cotunnite phases of MgF 2 . In the present work, we find that the P bca O-I 'orthorhombic-I' structure, which has been reported experimentally for TiO 2 near 30 GPa [45], is also stable for MgF 2 between 39.6 and 44.1 GPa.…”

Section: Magnesium Difluoridementioning

confidence: 99%

High-pressure phases of group-II difluorides: Polymorphism and superionicity

Nelson¹,

Needs²,

Pickard³

2017

Phys. Rev. B

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We investigate the high-pressure behaviour of beryllium, magnesium and calcium difluorides using ab initio random structure searching and density functional theory (DFT) calculations, over the pressure range 0−70 GPa. Beryllium fluoride exhibits extensive polymorphism at low pressures, and we find two new phases for this compound − the silica moganite and CaCl2 structures − which are stable over the wide pressure range 12−57 GPa. For magnesium fluoride, our searching results show that the orthorhombic 'O-I' TiO2 structure (P bca, Z = 8) is stable for this compound between 40 and 44 GPa. Our searches find no new phases at the static-lattice level for calcium difluoride between 0 and 70 GPa; however, a phase with P 62m symmetry is close to stability over this pressure range, and our calculations predict that this phase is stabilised at high temperature. The P 62m structure exhibits an unstable phonon mode at large volumes which may signal a transition to a superionic state at high temperatures. The Group-II difluorides are isoelectronic to a number of other AB2-type compounds such as SiO2 and TiO2, and we discuss our results in light of these similarities.

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High-pressure structural phase transitions and intermediate phases of magnesium fluoride

Cited by 17 publications

References 32 publications

Phase transition of GeO2 crystal at high pressure: An ab initio molecular dynamics study

Phase transition of GeO2 crystal at high pressure: An ab initio molecular dynamics study

Reactivity of He with ionic compounds under high pressure

High-pressure phases of group-II difluorides: Polymorphism and superionicity

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