Editing Metallic hydrogen (section)

===Claimed observation of solid metallic hydrogen, 2016===
On 5 October 2016, [[Ranga P. Dias|Ranga Dias]] and Isaac F. Silvera of [[Harvard University]] released claims in a pre-print manuscript of experimental evidence that solid metallic hydrogen had been synthesized in the laboratory at a pressure of around {{convert|495|GPa|atm psi}} using a [[diamond anvil cell]].  A revised version was published in ''[[Science (journal)|Science]]'' in 2017.<ref name="DiasArxiv"><!-- deliberate link to arxiv version - don't update to the Science paper -->{{Cite arXiv<!--Deny Citation Bot-->|last1=Dias|first1=R.|last2=Silvera|first2=I. F.|date=2016|title=Observation of the Wigner-Huntington Transition to Solid Metallic Hydrogen|arxiv=1610.01634|class=cond-mat.mtrl-sci<!-- do not add |doi= -->}}</ref><ref name=":1">{{Cite journal |last1=Dias |first1=R. P. |last2=Silvera |first2=I. F. |date=2017 |title=Observation of the Wigner-Huntington transition to metallic hydrogen |journal=[[Science (journal)|Science]] |volume=355 |issue= 6326|pages=715–718 |arxiv=1610.01634 |bibcode=2017Sci...355..715D |doi=10.1126/science.aal1579 |pmid=28126728 |s2cid=52851498}}</ref><ref name=":0">{{Cite news |last=Crane |first=L. |date=26 January 2017 |title=Metallic hydrogen finally made in lab at mind-boggling pressure |newspaper=[[New Scientist]] |url=https://www.newscientist.com/article/2119442-metallic-hydrogen-finally-made-in-lab-at-mind-boggling-pressure/ |access-date=26 January 2017}}</ref>

In the preprint version of the paper, Dias and Silvera write:

{{Blockquote| text=With increasing pressure we observe changes in the sample, going from transparent, to black, to a reflective metal, the latter studied at a pressure of 495 GPa... the reflectance using a [[Drude Model|Drude free electron model]] to determine the plasma frequency of 30.1&nbsp;eV at ''T''&nbsp;=&nbsp;5.5&nbsp;K, with a corresponding electron carrier density of {{val|6.7|e=23}} particles/cm<sup>3</sup>, consistent with theoretical estimates. The properties are those of a metal. Solid metallic hydrogen has been produced in the laboratory. | | Dias & Silvera (2016)<ref name=DiasArxiv/>}}

In June 2019 a team at the [[Commissariat à l'énergie atomique et aux énergies alternatives]] (French Alternative Energies & Atomic Energy Commission) claimed to have created metallic hydrogen at around 425GPa.<ref>{{cite journal |last1=Loubeyre |first1=Paul |last2=Occelli |first2=Florent |last3=Dumas |first3=Paul |title=Synchrotron infrared spectroscopic evidence of the probable transition to metal hydrogen |journal=Nature |date=30 January 2020 |volume=577 |issue=7792 |pages=631–635 |doi=10.1038/s41586-019-1927-3|pmid=31996819 |bibcode=2020Natur.577..631L }}</ref>

W. Ferreira et al. (including Dias and Silvera) repeated their experiments multiple times after the Science article was published, finally publishing in 2023 and finding metallisation of hydrogen between {{convert|477 and 491|GPa|atm}}. This time, the pressure was released to assess the question of metastability. Metallic hydrogen was not found to be metastable to zero pressure.<ref>{{cite journal |last1=Ferreira |first1=W. C. |last2=Møller |first2=M. |last3=Linsuain |first3=K. |last4=Song |first4=J. |last5=Salamat |first5=A. |last6=Dias |first6=R. |last7=Silvera |first7=I. F. |title=Metallic hydrogen: Study of metastability |journal=APL Materials |date=1 December 2023 |volume=11 |issue=12 |doi=10.1063/5.0178261|bibcode=2023APLM...11l1116F |doi-access=free }}</ref>