solid oxygen
{{Short description|Oxygen in solid state}}
{{about|the solid phase of elemental oxygen|solids used as a source of oxygen or as an oxidizer|Oxidizing agent}}
Solid oxygen is the solid ice phase of oxygen. It forms below {{cvt|54.36|K}} at standard atmospheric pressure. Solid oxygen O2, like liquid oxygen, is a clear substance with a light sky-blue color caused by absorption in the red part of the visible light spectrum.
Oxygen molecules have a relationship between the molecular magnetization and crystal structures, electronic structures, and superconductivity. Oxygen is the only simple diatomic molecule (and one of the few molecules in general) to carry a magnetic moment. This makes solid oxygen particularly interesting, as it is considered a "spin-controlled" crystal{{cite journal |author1=Freiman, Y. A. |author2=Jodl, H. J. |name-list-style=amp |title=Solid oxygen |journal= Physics Reports|volume=401 |issue=1–4 |pages=1–228 |year=2004 |doi=10.1016/j.physrep.2004.06.002|bibcode = 2004PhR...401....1F }} that displays antiferromagnetic magnetic order in the low temperature phases. The magnetic properties of oxygen have been studied extensively.See also: For papers dealing with the magnetic properties of solid oxygen we refer to magnetisation of condensed oxygen under high pressures and in strong magnetic fields by R.J. Meier, C.J. Schinkel and A. de Visser, J. Phys. C15 (1982) 1015–1024, far infrared absorption dealing with the magnetic excitations or spinwaves in Meier R J, Colpa J H P and Sigg H 1984 J. Phys. C: Solid State Phys. 17 4501. At very high pressures, solid oxygen changes from an insulating to a metallic state;{{cite journal |author=Desgreniers, S., Vohra, Y. K. & Ruoff, A. L. |title=Optical response of very high density solid oxygen to 132 GPa |journal=The Journal of Physical Chemistry|volume=94 |pages=1117–1122 |year=1990 |doi=10.1021/j100366a020 |issue=3}} and at very low temperatures, it transforms to a superconducting state.{{cite journal |author=Shimizu, K., Suhara, K., Ikumo, M., Eremets, M. I. & Amaya, K. |s2cid=205001394 |title=Superconductivity in oxygen |journal=Nature |volume=393 |pages=767–769 |year=1998 |doi=10.1038/31656 |issue=6687 |bibcode=1998Natur.393..767S}} Structural investigations of solid oxygen began in the 1920s and, at present, six distinct crystallographic phases are established unambiguously.
The density of solid oxygen ranges from 21 cm3/mol in the α-phase, to 23.5 cm3/mol in the γ-phase.{{cite journal | doi = 10.1063/1.555582 | title = The molar volume (density) of solid oxygen in equilibrium with vapor | year = 1978 | last1 = Roder | first1 = H. M. | journal = Journal of Physical and Chemical Reference Data | volume = 7 | issue = 3 | pages = 949–958|bibcode = 1978JPCRD...7..949R }}
Phases
File:Phase diagram of solid oxygen.svg for solid oxygen]]
Six different phases of solid oxygen are known to exist:{{cite web |url=http://www.azonano.com/details.asp?ArticleID=1797|author=Advanced Industrial Science and Technology (AIST)|work= AZoNano|title=Solid Oxygen ε-Phase Crystal Structure Determined Along With The Discovery of a Red Oxygen O8 Cluster |accessdate=2008-01-10|date=2006}}
- α-phase: light blue{{snd}} forms at 1 atm, below 23.8 K, monoclinic crystal structure, space group C2/m (no. 12).
- β-phase: faint blue to pink{{snd}} forms at 1 atm, below 43.8 K, rhombohedral crystal structure, space group R{{overline|3}}m (no. 166). At room temperature and high pressure begins transformation to tetraoxygen.
- γ-phase: faint blue{{snd}} forms at 1 atm, below 54.36 K, cubic crystal structure, Pm{{overline|3}}n (no. 223).{{cite journal | last1=Jordan | first1=T. H. | last2=Streib | first2=W. D. | last3=Smith | first3=H. W. | last4=Lipscomb | first4=W. N. | title=Single-crystal studies of β-F2and of γ-O2 | journal=Acta Crystallographica | publisher=International Union of Crystallography (IUCr) | volume=17 | issue=6 | date=1964-06-01 | issn=0365-110X | doi=10.1107/s0365110x6400202x | pages=777–778| doi-access=free }}{{cite journal | last=DeFotis | first=Gary C. | title=Magnetism of solid oxygen | journal=Physical Review B | publisher=American Physical Society (APS) | volume=23 | issue=9 | date=1981-05-01 | issn=0163-1829 | doi=10.1103/physrevb.23.4714 | pages=4714–4740| bibcode=1981PhRvB..23.4714D }}
- δ-phase: orange{{snd}} forms at room temperature at a pressure of 9 GPa
- ε-phase: dark-red to black{{snd}} forms at room temperature at pressures greater than 10 GPa
- ζ-phase: metallic{{snd}} forms at pressures greater than 96 GPa
It has been found that oxygen is solidified into a state called the β-phase at room temperature by applying pressure, and with further increasing pressure, the β-phase undergoes phase transitions to the δ-phase at 9 GPa and the ε-phase at 10 GPa; and, due to the increase in molecular interactions, the color of the β-phase changes to pink, orange, then red (the stable octaoxygen phase), and the red color further darkens to black with increasing pressure. It was found that a metallic ζ-phase appears at 96 GPa when ε-phase oxygen is further compressed.
= Red oxygen =
{{Main|Octaoxygen}}
As the pressure of oxygen at room temperature is increased through {{convert|10|GPa|psi}}, it undergoes a dramatic phase transition. Its volume decreases significantly{{cite journal
| last1 = Akahama
| first1 = Yuichi
|first2=Haruki |last2=Kawamura |first3=Daniel |last3=Häusermann |first4=Michael |last4=Hanfland |first5=Osamu |last5=Shimomura
|date=June 1995
| title = New High-Pressure Structural Transition of Oxygen at 96 GPa Associated with Metallization in a Molecular Solid
| journal = Physical Review Letters
| volume = 74
| issue = 23
| pages = 4690–4694
| doi = 10.1103/PhysRevLett.74.4690
| pmid=10058574
| bibcode=1995PhRvL..74.4690A}} and it changes color from sky-blue to deep red.{{cite journal
| last1 = Nicol
| first1 = Malcolm
|first2=K. R. |last2=Hirsch |first3=Wilfried B. |last3=Holzapfel
|date=December 1979
| title = Oxygen Phase Equilibria near 298 K
| journal = Chemical Physics Letters
| volume = 68
| issue = 1
| pages = 49–52
| doi = 10.1016/0009-2614(79)80066-4
|bibcode = 1979CPL....68...49N }} However, this is a different allotrope of oxygen, {{chem|O|8}}, not merely a different crystalline phase of O2.
| class="wikitable" style="text-align:center;" | 170px |
| Ball-and-stick model of O8 | Part of the crystal structure of ε-oxygen |
= Metallic oxygen =
A ζ-phase appears at 96 GPa when ε-phase oxygen is further compressed. This phase was discovered in 1990 by pressurizing oxygen to 132 GPa. The ζ-phase with metallic cluster{{cite journal |journal= ChemPhysChem|volume=3 |issue=1 |pages=53–56 |date=2002-01-14 |first1=Peter P. |last1=Edwards |first2=Friedrich |last2=Hensel |title=Metallic Oxygen |publisher=WILEY-VCH-Verlag |location=Weinheim, Germany | doi=10.1002/1439-7641(20020118)3:1<53::AID-CPHC53>3.0.CO;2-2 |pmid=12465476}} exhibits superconductivity at pressures over 100 GPa and a temperature below 0.6 K.