Crystal structures and <i>P–T</i> phase diagrams of SrC2O5 and BaC2O5

Sagatova, Dinara N.; Gavryushkin, Pavel N.; Sagatov, Nursultan E.; Banaev, Maksim V.

doi:10.1002/jcc.27210

Cited by 10 publications

(6 citation statements)

References 40 publications

(133 reference statements)

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“…Speaking about the sp 3 structures of carbonates, it should be also mentioned the recently found intermediate compounds in the MO−CO 2 (M = Mg, Ca, Sr, Ba) and M′ 2 O−CO 2 (M′ = Li, Na, K) systems, including Mg 2 CO 4 , 14,15 Ca 2 CO 4 , 16,17 Sr 2 CO 4 , 6,18 6,20 Sr 3 CO 5 , 6,21 Ba 3 CO 5 6 and CaC 2 O 5 . 20,22,23 The sp 3 -hybridized structures of these compounds became thermodynamically stable at much lower pressures than sp 3 structures of classical carbonates. The pressures of stabilization vary in the range of 5−25 GPa.…”

Section: Introductionmentioning

confidence: 99%

First Finding of High-Pressure Modifications of Na₂CO₃ and K₂CO₃ with sp³-Hybridized Carbon Atoms

Gavryushkin,

Sagatov,

Sagatova

et al. 2023

Crystal Growth & Design

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The transition from structures with classical [CO 3 ] triangles to structures with [CO 4 ] tetrahedra, corresponding to the transition from sp 2 to sp 3 hybridization of carbon atoms, is quite well established for alkaline earth carbonates CaCO 3 and MgCO 3 . Here, using a crystal structure prediction technique, we show that alkali carbonates Na 2 CO 3 and K 2 CO 3 follow the same trend. Both compounds form isostructural sp 3 -hybridized phases, Na 2 CO 3 −C2/m and K 2 CO 3 −C2/m, which became thermodynamically stable at pressures above 125 and 150 GPa, respectively. The automated topological search through ICSD has shown that the found C2/m structures, as well as sp 3 -structures of CaCO 3 and MgCO 3 do not have topological analogs among silicates and phosphates. Transitions of Na 2 CO 3 and K 2 CO 3 to C2/m structures are realized without sufficient perturbation of the initial Na 2 CO 3 −P2 1 /m and K 2 CO 3 −P1̅ structures and require relatively small atomic displacements of carbon and oxygen atoms. These transitions are realized through simple energy optimization. This indicates the absence or low height of the energy barrier. In the wide interval of pressures before the transition to the sp 3 structures, carbon atoms of [CO 3 ] triangles are gradually displaced from the plane defined by three oxygen atoms due to the interaction with the fourth oxygen atom. In the case of Na 2 CO 3 , the dihedral angle C−O−O−O describing the degree of this displacement increases from 5 to 12°, when the pressure increases from 60 to 127 GPa. At pressures above 130 GPa, the angle abruptly increases to the value of 31°, which corresponds to the formation of the sp 3hybridized phase Na 2 CO 3 −C2/m. Based on the examples of alkali and alkaline earth carbonates, we show that the transition from a sp 2 -hybridized [CO 3 ] triangle to a sp 3 -hybridized [CO 4 ] tetrahedron is realized when the fourth oxygen atom approaches the carbon atom at a distance less than 2.0 Å, which is usually realized at pressures of around 100 GPa. The stable structures with sp 3 -hybridized carbon atoms have not been found for Li 2 CO 3 in the considered pressure range up to 200 GPa, and we show that the P6 3 /mcm structure of this compound is stable in sp 2 form up to a pressure of 700 GPa or even higher. This indicates that not all the structures of carbonates adopt sp 3 form even at extreme pressures.

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Section: Introductionmentioning

confidence: 99%

First Finding of High-Pressure Modifications of Na₂CO₃ and K₂CO₃ with sp³-Hybridized Carbon Atoms

Gavryushkin,

Sagatov,

Sagatova

et al. 2023

Crystal Growth & Design

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“…Its phase transition sequence is Cc (10 GPa) → I d 42 ̅ (21 GPa)→Fdd2 (59 GPa)→Pc and C2 (80 GPa) as pressure increases. In addition, other pyrocarbonates have been synthesized and predicted, such as SrC 2 O 5 [19,20], BaC 2 O 5 [20], PbC 2 O 5 [21,22], and MnC 2 O 5 [23]. The discovery of these new carbonates further enriched the types of carbonates.…”

Section: Introductionmentioning

confidence: 99%

Phase diagram and physical properties of pyrocarbonate CaC₂O₅: first-principles calculations

Guo,

Qi,

Liu

et al. 2024

Phys. Scr.

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Understanding the physical properties of Ca-carbonate at high pressure is crucial for comprehending the carbon cycle in the Earth's interior. Recently, a new pyrocarbonate, CaC2O5, has been discovered. In this work, we update the phase diagram of CaC2O5. The structure, elastic, and seismic properties of CaC2O5 polymorphs under lower mantle pressure are studied using first-principles calculations, and compared with those of orthocarbonate Ca2CO4. Our findings reveal that CaC2O5 may have four stable phases under lower mantle temperature and pressure conditions, namely the I42d, Fdd2, Pc, and C2 phases. The carbon may be stored in the new pyrocarbonate CaC2O5 polymorphs. The thermodynamic properties of CaC2O5-I42d are obtained by quasi-harmonic approximation. This work contributes to our understanding of the behavior of Ca-carbonate in the Earth's lower mantle conditions.

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“…14,15 New stable sp 3 -carbonate phases containing isolated [CO 4 ] 4− -tetrahedra (Na 4 [CO 4 ]) or chains of [CO 4 ] 4− -tetrahedra (Na 2 [CO 3 ]- C 2/ m ) have been predicted for sodium carbonate at elevated pressures, but the system Na 2 O–CO 2 has not been investigated experimentally up to now. 16,17…”

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confidence: 99%

High-pressure synthesis of acentric sodium pyrocarbonate, Na₂[C₂O₅]

Spahr,

Bayarjargal,

Bykov

et al. 2024

Dalton Trans.

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Crystal structures and P–T phase diagrams of SrC2O5 and BaC2O5

Cited by 10 publications

References 40 publications

First Finding of High-Pressure Modifications of Na₂CO₃ and K₂CO₃ with sp³-Hybridized Carbon Atoms

First Finding of High-Pressure Modifications of Na₂CO₃ and K₂CO₃ with sp³-Hybridized Carbon Atoms

Phase diagram and physical properties of pyrocarbonate CaC₂O₅: first-principles calculations

High-pressure synthesis of acentric sodium pyrocarbonate, Na₂[C₂O₅]

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Crystal structures and P–T phase diagrams of SrC2O5 and BaC2O5

Cited by 10 publications

References 40 publications

First Finding of High-Pressure Modifications of Na2CO3 and K2CO3 with sp3-Hybridized Carbon Atoms

First Finding of High-Pressure Modifications of Na2CO3 and K2CO3 with sp3-Hybridized Carbon Atoms

Phase diagram and physical properties of pyrocarbonate CaC2O5: first-principles calculations

High-pressure synthesis of acentric sodium pyrocarbonate, Na2[C2O5]

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First Finding of High-Pressure Modifications of Na₂CO₃ and K₂CO₃ with sp³-Hybridized Carbon Atoms

First Finding of High-Pressure Modifications of Na₂CO₃ and K₂CO₃ with sp³-Hybridized Carbon Atoms

Phase diagram and physical properties of pyrocarbonate CaC₂O₅: first-principles calculations

High-pressure synthesis of acentric sodium pyrocarbonate, Na₂[C₂O₅]