Abstract
Stability and compressibility of several nonmolecular (polymeric) CO2 solids in structures analogous to those of SiO2 have been investigated with ab initio density-functional theory. Contrary to the recent experimental reports of a "superhard" high-pressure tridymite form of CO2, we find that metastable tetrahedrally bonded CO2 polymorphs, such as tridymite, cristobalite, and quartz, are relatively compressible, with bulk moduli K of only 1/2 to 1/3 of the reported experimental value. In addition, theory finds that the experimentally reported lattice parameters are not stable for CO2 P212121 tridymite. Finally, none of the calculated x-ray spectra of the fully relaxed structures of CO2 polymorphs obtained from theory agrees with the experiments. The significant discrepancy between experiments and density-functional theory suggests that further studies on nonmolecular CO2 solids are necessary, and that the assumptions that density-functional theory can describe these materials correctly, or that the framework of the new nonmolecular CO2 solids contains only CO4 tetrahedra, must be re-examined.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 14685-14689 |
| Number of pages | 5 |
| Journal | Physical Review B - Condensed Matter and Materials Physics |
| Volume | 62 |
| Issue number | 22 |
| DOIs | |
| State | Published - Dec 1 2000 |
| Externally published | Yes |
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ASJC Scopus subject areas
- Condensed Matter Physics
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Investigation of hardness in tetrahedrally bonded nonmolecular CO2 solids by density-functional theory. / Dong, J.; Tomfohr, J. K.; Sankey, O. F.; Leinenweber, Kurt; Somayazulu, M.; McMillan, P. F.
In: Physical Review B - Condensed Matter and Materials Physics, Vol. 62, No. 22, 01.12.2000, p. 14685-14689.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Investigation of hardness in tetrahedrally bonded nonmolecular CO2 solids by density-functional theory
AU - Dong, J.
AU - Tomfohr, J. K.
AU - Sankey, O. F.
AU - Leinenweber, Kurt
AU - Somayazulu, M.
AU - McMillan, P. F.
PY - 2000/12/1
Y1 - 2000/12/1
N2 - Stability and compressibility of several nonmolecular (polymeric) CO2 solids in structures analogous to those of SiO2 have been investigated with ab initio density-functional theory. Contrary to the recent experimental reports of a "superhard" high-pressure tridymite form of CO2, we find that metastable tetrahedrally bonded CO2 polymorphs, such as tridymite, cristobalite, and quartz, are relatively compressible, with bulk moduli K of only 1/2 to 1/3 of the reported experimental value. In addition, theory finds that the experimentally reported lattice parameters are not stable for CO2 P212121 tridymite. Finally, none of the calculated x-ray spectra of the fully relaxed structures of CO2 polymorphs obtained from theory agrees with the experiments. The significant discrepancy between experiments and density-functional theory suggests that further studies on nonmolecular CO2 solids are necessary, and that the assumptions that density-functional theory can describe these materials correctly, or that the framework of the new nonmolecular CO2 solids contains only CO4 tetrahedra, must be re-examined.
AB - Stability and compressibility of several nonmolecular (polymeric) CO2 solids in structures analogous to those of SiO2 have been investigated with ab initio density-functional theory. Contrary to the recent experimental reports of a "superhard" high-pressure tridymite form of CO2, we find that metastable tetrahedrally bonded CO2 polymorphs, such as tridymite, cristobalite, and quartz, are relatively compressible, with bulk moduli K of only 1/2 to 1/3 of the reported experimental value. In addition, theory finds that the experimentally reported lattice parameters are not stable for CO2 P212121 tridymite. Finally, none of the calculated x-ray spectra of the fully relaxed structures of CO2 polymorphs obtained from theory agrees with the experiments. The significant discrepancy between experiments and density-functional theory suggests that further studies on nonmolecular CO2 solids are necessary, and that the assumptions that density-functional theory can describe these materials correctly, or that the framework of the new nonmolecular CO2 solids contains only CO4 tetrahedra, must be re-examined.
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U2 - 10.1103/PhysRevB.62.14685
DO - 10.1103/PhysRevB.62.14685
M3 - Article
VL - 62
SP - 14685
EP - 14689
JO - Physical Review B-Condensed Matter
JF - Physical Review B-Condensed Matter
SN - 0163-1829
IS - 22
ER -