High-pressure transformations of CaC2O5– a full structural trend from double [CO3] triangles through the isolated group of [CO4] tetrahedra to framework and layered structures

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

doi:10.1039/d2cp01748b

Cited by 10 publications

(24 citation statements)

References 41 publications

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“…Then, in our recent work at pressures of 10 GPa, we predicted a new modification CaC 2 O 5 -Cc, the structure of which contains [C 2 O 5 ] 2À pyro-groups. 17 This structural feature was first demonstrated for SrC 2 O 5 -P2 1 =c. 11 Pyrocarbonate SrC 2 O 5 -P2 1 =c was synthesized from SrCO 3 and CO 2 at 30 GPa and 2000 K in an LH-DAC.…”

mentioning

confidence: 84%

“…Using of two fundamentally different approaches will allow a more detailed and high-quality screening of structures with the lowest formation energy. 2,17 First, the search was performed using the AIRSS package. On average, 3000-3500 structures were randomly generated and optimized at each pressure, and then those with the lowest enthalpy were selected.…”

Section: Methodsmentioning

confidence: 99%

“…These structures are isostructural to high-pressure modifications of CaC 2 O 5 . 1,17 In the next step, in order to determine the dynamic stability of the considered structures the phonon dispersion curves were calculated.…”

Section: Methodsmentioning

confidence: 99%

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

Sagatova,

Gavryushkin,

Sagatov

et al. 2023

J Comput Chem

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In this study, we present the results of a search for new stable structures of SrCO and BaCO in the pressure range of 0–100 GPa based on the density functional theory and crystal structure prediction approaches. We have shown that the recently synthesized pyrocarbonate structure SrCO‐ is thermodynamically stable for both SrCO and BaCO. Thus, SrCO‐ is stable relative to decomposition reaction above 10 GPa, while the lower‐pressure stability limit for BaCO‐ is 5 GPa, which is the lowest value for the formation of pyrocarbonates. For SrCO, the following polymorphic transitions were found with increasing pressure: at 40 GPa and 1000 K, at 90 GPa and 1000 K. SrCO‐ and SrCO‐ are characterized by the framework and layered structures of [CO] tetrahedra, respectively. For BaCO, with increasing pressure, decomposition of BaCO‐ into BaCO and CO is observed at 34 GPa without any polymorphic transitions.

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confidence: 84%

Section: Methodsmentioning

confidence: 99%

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

Sagatova,

Gavryushkin,

Sagatov

et al. 2023

J Comput Chem

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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 , , Ca 2 CO 4 , , Sr 2 CO 4 , , Ba 2 CO 4 , Li 4 CO 4 , Na 4 CO 4 , K 4 CO 4 , Ca 3 CO 5 , , Sr 3 CO 5 , , Ba 3 CO 5 and CaC 2 O 5 . ,, 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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“…[5][6][7][8][9][10][11] However, at the moment, it is an open question which pyrocarbonates can be synthesized. For example, a Capyrocarbonate (Ca[C 2 O 5 ]) has been predicted, 12 however, at conditions at which pyrocarbonates are typically formed, experiments yielded instead the sp 3 -carbonate CaC 2 O 5 , in which the carbon is tetrahedrally coordinated by oxygen. 13 In order to anticipate, whether pyrocarbonates can be chemically diverse, it is important to understand how rigid the [C 2 O 5 ] 2Àgroups are.…”

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confidence: 99%

Twisted [C₂O₅]²⁻-groups in Ba[C₂O₅] pyrocarbonate

Spahr,

Bayarjargal,

Haussühl

et al. 2023

Chem. Commun.

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High-pressure transformations of CaC₂O₅– a full structural trend from double [CO₃] triangles through the isolated group of [CO₄] tetrahedra to framework and layered structures

Abstract: Over the past few years, the concept of carbonates, as the salts of MCO3 or M'2CO3 composition with [CO3] triangles in the crystal structures was sufficiently extended. In addition to...

Cited by 10 publications

References 41 publications

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

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

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

Twisted [C₂O₅]²⁻-groups in Ba[C₂O₅] pyrocarbonate

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High-pressure transformations of CaC2O5– a full structural trend from double [CO3] triangles through the isolated group of [CO4] tetrahedra to framework and layered structures

Abstract: Over the past few years, the concept of carbonates, as the salts of MCO3 or M'2CO3 composition with [CO3] triangles in the crystal structures was sufficiently extended. In addition to...

Cited by 10 publications

References 41 publications

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

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

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

Twisted [C2O5]2−-groups in Ba[C2O5] pyrocarbonate

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High-pressure transformations of CaC₂O₅– a full structural trend from double [CO₃] triangles through the isolated group of [CO₄] tetrahedra to framework and layered structures

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

Twisted [C₂O₅]²⁻-groups in Ba[C₂O₅] pyrocarbonate