Structural Evolution of Carbon Dioxide under High Pressure

Lu, Cheng; Miao, Maosheng; Ma, Yanming

doi:10.1021/ja404854x

Cited by 120 publications

(68 citation statements)

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“…of CO 2 (named here CO 2 -V′) in which all C atoms are sp 3 hybridized with bridging O atoms. Note that this structure is different from another previously predicted fourfold coordinated structure (20) coincidentally with the same Pna2 1 space group but with 4 f.u.…”

Section: Structural Alchemy Of Phase V (Co 2 -V)contrasting

confidence: 95%

Crystal structures and dynamical properties of dense CO ₂

Yong

Liu

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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Structural polymorphism in dense carbon dioxide (CO 2 ) has attracted significant attention in high-pressure physics and chemistry for the past two decades. Here, we have performed high-pressure experiments and first-principles theoretical calculations to investigate the stability, structure, and dynamical properties of dense CO 2 . We found evidence that CO 2 -V with the 4-coordinated extended structure can be quenched to ambient pressure below 200 K-the melting temperature of CO 2 -I. CO 2 -V is a fully coordinated structure formed from a molecular solid at high pressure and recovered at ambient pressure. Apart from confirming the metastability of CO 2 -V (I-42d) at ambient pressure at low temperature, results of ab initio molecular dynamics and metadynamics (MD) simulations provided insights into the transformation processes and structural relationship from the molecular to the extended phases. In addition, the simulation also predicted a phase V′(Pna2 1 ) in the stability region of CO 2 -V with a diffraction pattern similar to that previously assigned to the CO 2 -V (P2 1 2 1 2 1 ) structure. Both CO 2 -V and -V′ are predicted to be recoverable and hard with a Vicker hardness of ∼20 GPa. Significantly, MD simulations found that the CO 2 in phase IV exhibits large-amplitude bending motions at finite temperatures and high pressures. This finding helps to explain the discrepancy between earlier predicted static structures and experiments. MD simulations clearly indicate temperature effects are critical to understanding the high-pressure behaviors of dense CO 2 structures-highlighting the significance of chemical kinetics associated with the transformations.carbon dioxide | molecular dynamics | high pressure | material science S olid carbon dioxide (CO 2 ) has a phase diagram rich in polymorphs, which exhibit great diversity in intermolecular interactions, chemical bonding, and crystal structures (1-7). Colloquially known as dry ice, solid CO 2 has a cubic Pa3 structure (phase I) under ambient pressure (8). At around 10 GPa, the cubic structure transforms to another molecular phase (Cmca, phase III) with different stacking pattern of CO 2 molecules. At sufficient compression, the molecular O = C = O bonds in solid CO 2 are replaced by an extended network of single C-O bonds, forming CO 4 tetrahedral units with sp 3 hybridized carbon atoms. The onset of such transformation occurs at 20 GPa, where the phase III transforms to a pseudotetragonal phase II (P4 2 /mnm or Pnnm) above ∼500 K and then to phase IV (P4 1 2 1 2 β-cristobalite structure) above ∼750 K (9-12). Continuing the compression to 40 GPa and then heating the product to 1,800 K, CO 2 further transforms to a nonmolecular polymeric strucutre V TD with the tridymite-like P2 1 2 1 2 1 structure (13, 14). Interestingly, following a different synthesis path, that is, heating the phase III first at 20 GPa and then compressing the product to 39 GPa and heating it again to ∼1,800 K, a different polymeric phase (CO 2 -V CR ) in a β-cristobalite-like I-42d structu...

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Section: Structural Alchemy Of Phase V (Co 2 -V)contrasting

confidence: 95%

Crystal structures and dynamical properties of dense CO ₂

Yong

Liu

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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“…1a,b. Our calculations recovered all the stable compounds known from previous crystal structure prediction works10111217212223. The crystal structures we obtained were either the same as those previously reported, or structurally and enthalpically (typically within 1 meV/atom) similar.…”

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confidence: 67%

“…This trend can be seen as a pressure-induced destabilization of the double bond, which is likely to be an important factor contributing to the polymerization of carbonic acid. The latter is indeed associated with the breaking of the π bond and the concurrent formation of a new C-O σ bond, in a way which is reminiscent of the high-pressure behavior of CO 2 10. Accordingly, upon the Pnma → Cmc2 1 phase transition, C-O bonds elongate and their ellipticity at bcp decreases (Table 1).…”

mentioning

confidence: 95%

“…have higher Gibbs free energy than an isochemical mixture of C, H, O, H 2 O, CO 2 , CH 4 . While H 2 O and CO 2 are expected to survive even in the terapascal regime1011, above 155 GPa methane was predicted to decompose into mixtures of hydrogen and heavier hydrocarbons, namely ethane, butane and polyethylene12. On further compression, all alkanes transform into diamond-hydrogen mixtures1213.…”

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confidence: 99%

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Novel Stable Compounds in the C-H-O Ternary System at High Pressure

Saleh

Oganov

2016

Sci Rep

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The chemistry of the elements is heavily altered by high pressure, with stabilization of many new and often unexpected compounds, the emergence of which can profoundly change models of planetary interiors, where high pressure reigns. The C-H-O system is one of the most important planet-forming systems, but its high-pressure chemistry is not well known. Here, using state-of-the-art variable-composition evolutionary searches combined with quantum-mechanical calculations, we explore the C-H-O system at pressures up to 400 GPa. Besides uncovering new stable polymorphs of high-pressure elements and known molecules, we predicted the formation of new compounds. A 2CH4:3H2 inclusion compound forms at low pressure and remains stable up to 215 GPa. Carbonic acid (H2CO3), highly unstable at ambient conditions, was predicted to form exothermically at mild pressure (about 1 GPa). As pressure rises, it polymerizes and, above 314 GPa, reacts with water to form orthocarbonic acid (H4CO4). This unexpected high-pressure chemistry is rationalized by analyzing charge density and electron localization function distributions, and implications for general chemistry and planetary science are also discussed.

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“…At present pressures up to 200 GPa are routinely achieved in diamond anvil cells (DACs), and the large influence of such high-pressure (HP) conditions on the properties and reactivity of the elements and chemical compounds is well documented15161718. The potential of obtaining novel species through the application of HP is exemplified inter alia by the recent synthesis of nitrogen analogues of alkanes19, or by the theoretical predictions that hypervalent carbon species can be stabilized at large compression20.…”

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confidence: 99%

Hexacoordinated nitrogen(V) stabilized by high pressure

Kurzydłowski

Zaleski‐Ejgierd

2016

Sci Rep

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In all of its known connections nitrogen retains a valence shell electron count of eight therefore satisfying the golden rule of chemistry - the octet rule. Despite the diversity of nitrogen chemistry (with oxidation states ranging from + 5 to −3), and despite numerous efforts, compounds containing nitrogen with a higher electron count (hypervalent nitrogen) remain elusive and are yet to be synthesized. One possible route leading to nitrogen’s hypervalency is the formation of a chemical moiety containing pentavalent nitrogen atoms coordinated by more than four substituents. Here, we present theoretical evidence that a salt containing hexacoordinated nitrogen(V), in the form of an NF6− anion, could be synthesized at a modest pressure of 40 GPa (=400 kbar) via spontaneous oxidation of NF3 by F2. Our results indicate that the synthesis of a new class of compounds containing hypervalent nitrogen is within reach of current high-pressure experimental techniques.

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Structural Evolution of Carbon Dioxide under High Pressure

Cited by 120 publications

References 39 publications

Crystal structures and dynamical properties of dense CO ₂

Crystal structures and dynamical properties of dense CO ₂

Novel Stable Compounds in the C-H-O Ternary System at High Pressure

Hexacoordinated nitrogen(V) stabilized by high pressure

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Structural Evolution of Carbon Dioxide under High Pressure

Cited by 120 publications

References 39 publications

Crystal structures and dynamical properties of dense CO 2

Crystal structures and dynamical properties of dense CO 2

Novel Stable Compounds in the C-H-O Ternary System at High Pressure

Hexacoordinated nitrogen(V) stabilized by high pressure

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Product

Resources

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Crystal structures and dynamical properties of dense CO ₂

Crystal structures and dynamical properties of dense CO ₂