Journal article
Crystal structures and dynamical properties of dense CO2
Proceedings of the National Academy of Sciences - PNAS, Vol.113(40), pp.11110-11115
10/04/2016
Handle:
https://hdl.handle.net/2376/112681
PMCID: PMC5056093
PMID: 27647887
Abstract
Using multiple theoretical techniques, the temperature and pressure dependence of the structures and dynamics of dense CO
2
were investigated. Near the transition to the extended structure, CO
2
molecules were found to exhibit large-amplitude bending vibrations. A 4-coordinated
Pna
2
1
structure (CO
2
-V′) with a diffraction pattern similar to CO
2
-V (
P2
1
2
1
2
1
) was found. Both CO
2
-V and -V′ are predicted to be metastable at ambient pressure. This result is in agreement with the experimental recovery of CO
2
-V below 200 K at ambient pressure. This 4-coordinated structure formed from main group molecules was recovered from high pressure. Both recovered fully extended CO
2
solids possess high- energy density and hardness.
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′(
Pna
2
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.
Metrics
9 Record Views
Details
- Title
- Crystal structures and dynamical properties of dense CO2
- Creators
- Xue Yong - Department of Physics and Engineering PhysicsHanyu Liu - Department of Physics and Engineering PhysicsMin Wu - College of Materials Science and EngineeringYansun Yao - Department of Physics and Engineering PhysicsJohn S Tse - Department of Physics and Engineering PhysicsRanga Dias - Department of ChemistryChoong-Shik Yoo - Department of Chemistry
- Publication Details
- Proceedings of the National Academy of Sciences - PNAS, Vol.113(40), pp.11110-11115
- Academic Unit
- Institute for Shock Physics
- Publisher
- National Academy of Sciences
- Grant note
- 1203834 / NSF | MPS | Division of Materials Research (DMR) W31P4Q-12-1-0009 / Defense Sciences Office, DARPA (DARPA Defense Science Office)
- Identifiers
- 99900548284601842
- Language
- English
- Resource Type
- Journal article