Carbon Dioxide at High Pressure and Temperature

Iota, V.; Yoo, Choong Shik

doi:10.1002/1521-3951(200101)223:2<427::aid-pssb427>3.0.co;2-q

Cited by 11 publications

(9 citation statements)

References 20 publications

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“…These results obtained from fully dynamical simulations reveal hitherto unknown microscopic transformation mechanisms, and illustrate the transformation from a molecular solid characterized by intramolecular -bonding to polymerized structure. The absence of intermediate structures with bent molecules in this study indicates that the transformation from molecular to nonmolecular phases could be structurally more abrupt than speculated (6,29). The transformation takes place at pressures within the range of those found in the Earth's mantle, where significant amounts of oxidized carbon are thought to be present, either in the form of carbonates or as a fluid (32,33).…”

Section: Discussionmentioning

confidence: 87%

“…T he search for high-pressure structures of CO 2 has resulted in numerous experimental reports and theoretical predictions over the last several decades (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14). There are many reasons for the large number of studies on this molecular system characterized by weak intermolecular bonding in the solid state at low pressures.…”

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confidence: 99%

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High-pressure polymeric phases of carbon dioxide

Sun

Klug²,

Martoňák³

et al. 2009

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

110

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Understanding the structural transformations of solid CO2 from a molecular solid characterized by weak intermolecular bonding to a 3-dimensional network solid at high pressure has challenged researchers for the past decade. We employ the recently developed metadynamics method combined with ab initio calculations to provide fundamental insight into recent experimental reports on carbon dioxide in the 60 -80 GPa pressure region. Pressure-induced polymeric phases and their transformation mechanisms are found. Metadynamics simulations starting from the CO 2-II (P42/mnm) at 60 GPa and 600 K proceed via an intermediate, partially polymerized phase, and finally yield a fully tetrahedral, layered structure (P-4m2). Based on the agreement between calculated and experimental Raman and X-ray patterns, the recently identified phase VI solid CO2 ͉ first-principles molecular dynamics ͉ metadynamics ͉ phase transition ͉ density functional theory T he search for high-pressure structures of CO 2 has resulted in numerous experimental reports and theoretical predictions over the last several decades (1-14). There are many reasons for the large number of studies on this molecular system characterized by weak intermolecular bonding in the solid state at low pressures. There is the distinct possibility that CO 2 may convert to a 3-dimensional network solid that is extraordinarily hard and light, at high pressures. It has also been suggested that CO 2 may be present in the Earth's mantle with structures that are similar or identical to structures of SiO 2 having either 4-or 6-coordinated carbon atoms (12). There are many remaining unresolved issues relating to the detailed structure of solid CO 2 and changes in the chemical bonding that may occur at high pressures. These include questions about the transformation from a quadrupolar molecular solid to an extended network structure, the onset of the bending of the CO 2 linear molecule, and the structural relationship to other materials such as SiO 2 .At moderate temperatures up to Ϸ700 K, and pressures of 50-80 GPa, transformations from the molecular phases are reported yielding a stishovite-like P4 2 /mnm structure (1) starting with molecular phase II of CO 2 . However, the stishovite-like structure is energetically unfavorable and mechanically unstable according to first-principles calculations (15). There is also a recent report indicating that CO 2 transforms at moderately high temperatures from the Cmca phase III to a network-forming amorphous phase (2, 3) with mixed 3-and 4-coordinated carbon atoms (15). At high temperatures, the Cmca phase III was reported to transform to a ''superhard'' material (7, 8). Theoretical investigations have predicted and examined a variety of competing phases with structures ranging from those found in SiO 2 to a layered HgI 2 -type structure (7,9,11,12). Theoretical studies have generally used density-functional methods such as total-energy calculations and relaxations and constant-pressure molecular dynamics. Total-energy calculations provide accura...

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Section: Discussionmentioning

confidence: 87%

mentioning

confidence: 99%

High-pressure polymeric phases of carbon dioxide

Sun

Klug²,

Martoňák³

et al. 2009

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

110

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“…Since the hardness of a compound is strictly connected to the presence in the network of light elements, CO 2 becomes an excellent candidate to produce ultrahard materials. This extended covalent solid (commonly labelled as phase V) can be obtained at relatively moderate pressure and temperature values [1], even though the first synthesis of this material was realized at temperatures exceeding 1000 K [2][3][4]. Following its discovery, a renewed interest arose for all the high-pressure high-temperature CO 2 polymorphs since these phases could be possibly interpreted as intermediate steps in a continuous transformation from the molecular phase I to the extended nonmolecular phase V [2].…”

Section: Introductionmentioning

confidence: 90%

“…An unusually large bulk modulus (87 GPa) has been reported for phase III [3,5]. Above 12 GPa two different phases, II [6] and IV [4], are observed on increasing temperature. The structures of these two phases could not be solved exactly and were suggested to be tetragonal or orthorhombic [7,8].…”

Section: Introductionmentioning

confidence: 99%

“…The structures of these two phases could not be solved exactly and were suggested to be tetragonal or orthorhombic [7,8]. A strong modification in the intermolecular interactions was proposed for both phases leading to a dimeric association of the molecules in phase II [7], and a large molecular bending in phase IV [4,8,9] as suggested by the Raman activation of the bending mode. These changes were interpreted as a prelude to the breaking of the double C=O bond and the formation of new covalent bonds between different molecules occurring in phase V. This interpretation has been recently contested in a DFT calculation by Bonev et al [10], which claimed a molecular character for all these phases (III, II and IV).…”

Section: Introductionmentioning

confidence: 99%

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Infrared study of high-pressure molecular phases of carbon dioxide

Giordano

Gorelli²,

Bini

2006

Low Temperature Physics

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The infrared absorption spectra of the high-pressure crystalline phases II, III and IV of solid CO 2 were studied by using a resistive heated diamond anvil cell up to 30 GPa. The employment of crystal slabs having thickness of~2 mm allowed the study of the strongly absorbing fundamental bending and antisymmetric stretching modes without saturation. These are the first data for phases II and IV in the fundamental modes spectral region, furthermore the high samples quality allowed to improve, with respect to previous studies, the characterization of the infrared spectra of phases I and III. The comparison of the spectral structure and of the frequency evolution with pressure of the crystal modes between phase I and the higher pressure phases clearly indicates the close resemblance among all these phases. In particular, the dramatic change of the intermolecular interaction claimed for phases II (dimeric association) and IV (large molecular bending) can be ruled out and, as a consequence, the hypothesis of a transition from the molecular phase I to the silica-like phase V through intermediate nonmolecular phases discarded.

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Binäre Stickstoffverbindungen der Hauptgruppenelemente durch Hochdrucksynthesen

Kroke

2002

Angew. Chem.

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Carbon Dioxide at High Pressure and Temperature

Cited by 11 publications

References 20 publications

High-pressure polymeric phases of carbon dioxide

High-pressure polymeric phases of carbon dioxide

Infrared study of high-pressure molecular phases of carbon dioxide

Binäre Stickstoffverbindungen der Hauptgruppenelemente durch Hochdrucksynthesen

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