from the what-do-you-*call*-NaHe2...-sodium-diheliunate? dept.
Helium, an "inert" noble gas, can form bonds with sodium at high pressure:
It's a surprising finding, he says, because, on Earth, helium is a chemically inert and unreactive compound that eschews connections with other elements and compounds. The first of the noble gases, helium features an extremely stable, closed-shell electronic configuration, leaving no openings for connections. Further, Boldyrev's colleagues confirmed computationally and experimentally that sodium, never an earthly comrade to helium, readily bonds with the standoffish gas under high pressure to form the curious Na2He compound. These findings were so unexpected, Boldyrev says, that he and colleagues struggled for more than two years to convince science reviewers and editors to publish their results.
Persistence paid off. Boldyrev and his doctoral student Ivan Popov, as members of an international research group led by Artem Oganov of Stony Brook University, published the pioneering findings in the Feb. 6, 2017, issue of Nature Chemistry [DOI: 10.1038/nchem.2716] [DX]. The USU chemists' participation in the project was supported by the National Science Foundation and the Ministry of Education and Science of the Russian Federation.
Boldyrev and Popov's role in the project was to interpret a chemical bonding in the computational model developed by Oganov and the experimental results generated by Alexander Goncharov of the Carnegie Institution of Washington. Initially, the Na2He compound was found to consist of Na8 cubes, of which half were occupied by helium atoms and half were empty. "Yet, when we performed chemical bonding analysis of these structures, we found each 'empty' cube actually contained an eight-center, two-electron bond," Boldyrev says. "This bond is what's responsible for the stability of this enchanting compound."
From the abstract: "We also predict the existence of Na2HeO with a similar structure at pressures above 15 GPa."
(Score: 3, Funny) by Anonymous Coward on Saturday February 11 2017, @08:10PM
> helium is a chemically inert and unreactive compound that eschews connections with other elements and compounds.
First time through I saw,
helium is a chemically inert and unattractive compound that eschews connections with other elements and compounds.
Helium, the social loser of the elements.
(Score: 1, Funny) by Anonymous Coward on Sunday February 12 2017, @03:12AM
That makes carbon a slut.
(Score: 2) by takyon on Saturday February 11 2017, @08:26PM
Wikipedia is calling it disodium helide, but I don't see anyone else using the name.
https://en.wikipedia.org/wiki/Helium_compounds [wikipedia.org]
And it's Na2He not NaHe2.
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(Score: 0) by Anonymous Coward on Sunday February 12 2017, @12:07AM
How do Helium bonds compare to convertible bonds and Inflation-indexed bonds?
Could we say that a helium bond without sodium at high pressure is more or less like a zero coupon bond?
(Score: 2) by fritsd on Saturday February 11 2017, @08:45PM
So.. IIRC..
one cube of Na_8
one cube of Na_8 He nextdoor; take 4 Na vertices away, gives:
Na_12 He for 2 cubes together; the Helium can tunnel to the other cube "room" if it gets bored.
Remove back wall of the two cubes: Na_12 He - Na_6 = Na_6 He
Remove ceiling of the two cubes Na_6 He - Na_3 = Na_3 He
Lastly, remove the right wall of the two cubes: Na_3 He - Na = Na_2 He
Kiss him .. Goodbye!
Now you have defined the unit cell.
So if you put 2 Na atoms flat, at distance r, then the Helium goes to the right of the second Na, distance 1/2 r right, back, and up.
Then repeat this rectangular 2r * r * r unit cell Avogadro times :-)
What I'm wondering is: how do these Heliums influence the ones in neighbouring unit cells? They must be able to tunnel through the Sodium maze quite easily.
And how weird that there are chemical bonds, but no actual atom to bond *TO*. "This space intentionally left blank".
(Score: 2) by takyon on Saturday February 11 2017, @08:49PM
https://en.wikipedia.org/wiki/Van_der_Waals_force [wikipedia.org]
However, I don't think the research is calling this a Van der Waals molecule. At least, not in the abstract.
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(Score: 0) by Anonymous Coward on Sunday February 12 2017, @04:17PM
One of my chemistry professors used to say that if you ever wanted a Nobel Prize, then all you had to do was get Helium to react with something. I'll be happy to see if he's right.