Editing Diamond anvil cell (section)

{{Short description|Device for generating extremely high pressures}}
[[Image:Diamond Anvil Cell - Cross Section.svg|upright=1.2|thumb|Schematics of the core of a diamond anvil cell. The culets (tip) of the two diamond anvils are typically 100–250&nbsp;[[micrometre|μm]] across.]]

A '''diamond anvil cell''' ('''DAC''') is a [[high-pressure]] device used in [[geology]], [[engineering]], and [[materials science]] [[Experiment|experiments]]. It permits the compression of a small (sub-[[millimeter]]-sized) piece of material to [[Orders of magnitude (pressure)|extreme pressure]]s, typically up to around 100–200&nbsp;[[Pascal (unit)|gigapascals]], although it is possible to achieve pressures up to 770&nbsp;[[Pascal (unit)|gigapascals]] (7,700,000&nbsp;[[bar (unit)|bars]] or 7.7&nbsp;million [[atmosphere (unit)|atmospheres]]).<ref>{{cite news |url=http://physicsworld.com/cws/article/news/2012/nov/02/improved-diamond-anvil-cell-allows-higher-pressures-than-ever-before |title=Improved diamond anvil cell allows higher pressures |magazine=Physics World |date=2 November 2012}}</ref><ref>{{cite news |url=https://www.sciencedaily.com/releases/2015/08/150824114555.htm |title=Record high pressure squeezes secrets out of osmium: X-ray experiments reveal peculiar behaviour of the most incompressible metal on Earth |work=ScienceDaily |access-date=2018-10-10}}</ref>

The device has been used to recreate the pressure existing deep inside [[planet]]s to synthesize materials and [[Phase (matter)|phases]] not observed under normal ambient conditions. Notable examples include the non-molecular [[ice X]],<ref>{{cite journal |last1=Goncharov |first1=A.F. |last2=Struzhkin |first2=V.V. |last3=Somayazulu |first3=M.S. |last4=Hemley |first4=R.J. |last5=Mao |first5=H.K. |date=July 1986 |title=Compression of ice to 210&nbsp;gigapascals: Infrared evidence for a symmetric hydrogen-bonded phase |journal=[[Science (journal)|Science]] |volume=273 |issue=5272 |pages=218–230 |doi=10.1126/science.273.5272.218 |pmid=8662500 |bibcode=1996Sci...273..218G|s2cid=10364693 }}</ref> polymeric nitrogen<ref>{{cite journal |title=Semiconducting non-molecular nitrogen up to 240&nbsp;GPa and its low-pressure stability |journal=[[Nature (journal)|Nature]] |date=May 2001 |volume=411 |issue=6834 |pages=170–174 |last1=Eremets |first1=M.I. |last2=Hemley |first2=R.J. |last3=Mao |first3=H.K. |last4=Gregoryanz |first4=E. |pmid=11346788 |doi=10.1038/35075531 |bibcode=2001Natur.411..170E |s2cid=4359193 }}</ref> and metallic phases of [[xenon]],<ref>{{cite journal |author1=Caldwell, W.A. |year=1997 |author2=Nguyen, J. |author3=Pfrommer, B. |author4=Louie, S. |authorlink5=Raymond Jeanloz |author5=Jeanloz, R. |title=Structure, bonding and geochemistry of xenon at high pressures |journal=[[Science (journal)|Science]] |volume=277 |issue=5328 |pages=930–933 |doi=10.1126/science.277.5328.930}}</ref> [[lonsdaleite]], and potentially [[metallic hydrogen]].<ref>
{{cite journal
 |last=Castelvecchi |first=D.
 |year=2017
 |title=Physicists doubt bold report of metallic hydrogen
 |journal=[[Nature (journal)|Nature]]
 |volume=542 |issue=7639 |page=17
 |bibcode=2017Natur.542...17C
 |doi=10.1038/nature.2017.21379
 |pmid=28150796
 |doi-access=free
}}</ref>

A DAC consists of two opposing [[diamond]]s with a sample compressed between the polished [[culet]]s (tips). Pressure may be monitored using a reference material whose behavior under pressure is known. Common pressure standards include [[Ruby pressure scale|ruby fluorescence]],<ref name="Forman1972">{{cite journal |last1=Forman |first1=Richard A. |last2=Piermarini |first2=Gasper J. |last3=Barnett |first3=J. Dean |last4=Block |first4=Stanley |year=1972 |title=Pressure measurement made by the utilization of ruby sharp-line luminescence |journal=Science |volume=176 |issue=4032 |pages=284–285 |bibcode=1972Sci...176..284F |doi=10.1126/science.176.4032.284 |pmid=17791916 |s2cid=8845394}}</ref> and various [[Crystal structure|structurally]] simple metals, such as [[copper]] or [[platinum]].<ref name="isbn0-12-408950-X">{{cite book |author1=Kinslow, Ray |author2=Cable, A.J. |title=High-velocity impact phenomena |publisher=Academic Press |location=Boston |year=1970 |isbn=978-0-12-408950-1}}</ref> The uniaxial pressure supplied by the DAC may be transformed into uniform [[Fluid statics#Hydrostatic pressure|hydrostatic pressure]] using a pressure-transmitting medium, such as [[argon]], [[xenon]], [[hydrogen]], [[helium]], [[Alkane|paraffin oil]] or a mixture of [[methanol]] and [[ethanol]].<ref name="jay1">{{cite journal |author=Jayaraman, A. |title=Ultrahigh pressures |journal=Review of Scientific Instruments |volume=57 |issue=6 |pages=1013–1031 |year=1986 |doi=10.1063/1.1138654 |bibcode=1986RScI...57.1013J}}</ref> The pressure-transmitting medium is enclosed by a gasket and the two diamond anvils. The sample can be viewed through the diamonds and illuminated by [[X-rays]] and visible light. In this way, [[X-ray diffraction]] and [[X-ray fluorescence|fluorescence]]; [[optical absorption]] and [[photoluminescence]]; [[Mössbauer spectroscopy|Mössbauer]], [[Raman scattering|Raman]] and [[Brillouin scattering]]; [[Positron annihilation spectroscopy|positron annihilation]] and other signals can be measured from materials under high pressure. Magnetic and microwave fields can be applied externally to the cell allowing [[nuclear magnetic resonance]], [[electron paramagnetic resonance]] and other magnetic measurements.<ref>{{cite journal |doi=10.1063/1.1143596 |title=Enhanced sensitivity for high-pressure EPR using dielectric resonators |year=1992 |last1=Bromberg |first1=Steven E. |last2=Chan |first2=I.Y. |journal=Review of Scientific Instruments |volume=63 |issue=7 |page=3670 |bibcode=1992RScI...63.3670B}}</ref> Attaching [[electrodes]] to the sample allows electrical and [[Magnetoresistance|magnetoelectrical]] measurements as well as heating up the sample to a few thousand degrees. Much higher temperatures (up to 7000 K)<ref>{{cite journal |last1=Chandra Shekar |first1=N.V. |display-authors=etal |year=2003 |title=Laser-heated diamond-anvil cell (LHDAC) in materials science research |journal=  Journal of Materials Sciences and Technology|volume=19 |issue=6 |page=518 |url=http://www.jmst.org/EN/abstract/abstract6706.shtml}}</ref> can be achieved with laser-induced heating,<ref>{{cite journal |last1=Subramanian |first1=N. |display-authors=etal |year=2006 |title=Development of laser-heated diamond anvil cell facility for synthesis of novel materials |url=http://www.iisc.ernet.in/currsci/jul252006/175.pdf |journal=Current Science |volume=91 |page=175}}</ref> and cooling down to millikelvins has been demonstrated.<ref name="jay1"/>