Thread: Zinc cyanide

argonne national labs applied extreem pressure to zinc cyanide and amazingly, it expands under pressure.

ok
that said:

Why does it "defy the laws of physics" in so doing---why does zinc cyanide expand under pressure ?

Are you sure it was zinc cyanide? I've never heard of anything like this for Zn(CN)₂, the related compound zinc dicyanoaurate does show this behaviour. I remember reading about it here:

Giant negative linear compressibility in zinc*dicyanoaurate : Nature Materials : Nature Publishing Group

If you don't have access to that article it is covered in this blog:

New transparent crystal expands under pressure | Science! | Geek.com

(You are on my ignore list but my interest in chemistry overrode it)

I read about it in a trade publication not a scientific journal, so ...accuracy of nomenclature remains in doubt.
they referenced "Science daily"

Thanks-will read linked material

ok

The team published the details of their work in the May 22 issue of the Journal of the American Chemical Society in an article titled “Exploiting High Pressures to Generate Porosity, Polymorphism, And Lattice Expansion in the Nonporous Molecular Framework Zn(CN)2 .”
The scientists put zinc cyanide - See more at: Discovery of new material state counterintuitive to laws of physics | Argonne National Laboratory

from:
Discovery of new material state counterintuitive to laws of physics | Argonne National Laboratory

and:

We certainly were never expecting anything to increase in volume,” says Karena Chapman of Argonne National Laboratory, who led the group that published these results recently in the Journal of the American Chemical Society. “I don’t think anyone would. It’s against the laws of physics for something to expand under pressure.”

Chapman and her colleagues managed to bend the laws of physics in this case by applying pressure to small fluid molecules—mainly methanol and water—surrounding the molecular framework material zinc cyanide, Zn(CN)2. The stable phase of zinc cyanide exists as tetrahedrally coordinated zinc ions bridged linearly by cyanide anions. Two of these frameworks interpenetrate in an overall non-porous, cubic system. At pressures of 0.9 to 1.8 GPa, the small molecules penetrated and induced reconstructive transitions in the zinc cyanide structure, replacing the interpenetrating networks with an open (non-interpentrating), porous structure with approximately twice the volume of the starting material. The liquid molecules wound up as guests in the pores of the new material. Using larger fluid molecules such as isopropanol or fluorinert as the pressurizing media led merely to compression of the starting zinc cyanide structure.

from:
Coordinated Framework Materials Expand Under Pressure - Materials360 Online

so, is this new to you?

really amazing?

Yep, news to me (materials science is not really my area of interest but I do tend to scan the Nature abstracts which is where I came across the article I linked to). I'll have a look at the links but from your quotes it appears to be due to forcing small molecules into the lattice which changes the structure.

Originally Posted by PhDemon

... from your quotes it appears to be due to forcing small molecules into the lattice which changes the structure.

That was my guess too........

caveat: as/re "guess" this is way outside my normal fields of study
imo basic research is often the underfunded orphan of science, and maybe the best?

Originally Posted by sculptor

argonne national labs applied extreem pressure to zinc cyanide and amazingly, it expands under pressure.

ok
that said:

Why does it "defy the laws of physics" in so doing---why does zinc cyanide expand under pressure ?

I don't think it defies the laws of physics. This looks like the usual journalists' hype. From what I read, it expands along one dimension. This would enable the material to respond to the pressure increase by reducing its overall volume (in accordance with "the laws of physics", but at the same time as extending itself along one axis.

But I'm open to correction, as I didn't now anything about the phenomenon until you alerted me to it.

Originally Posted by exchemist

Originally Posted by sculptor

argonne national labs applied extreem pressure to zinc cyanide and amazingly, it expands under pressure.

ok
that said:

Why does it "defy the laws of physics" in so doing---why does zinc cyanide expand under pressure ?

I don't think it defies the laws of physics. This looks like the usual journalists' hype. From what I read, it expands along one dimension. This would enable the material to respond to the pressure increase by reducing its overall volume (in accordance with "the laws of physics", but at the same time as extending itself along one axis.

But I'm open to correction, as I didn't now anything about the phenomenon until you alerted me to it.

exchemist:
From what I understood from what I read, the zinc cyanide expands in volume, not along one dimension(as in the zinc dicyanoaurate mentioned by PhDemon above).
Then, their reference to drying as part of industrial production process seems to support the idea that the expansion in volume is due to liquids being forced into the zinc cyanide making it sponge like. Which seems to be it's main value.

Yeh, me too: I'm open to correction;
and actually want it if/when I'm wrong.

Originally Posted by sculptor

Originally Posted by exchemist

Originally Posted by sculptor

argonne national labs applied extreem pressure to zinc cyanide and amazingly, it expands under pressure.

ok
that said:

Why does it "defy the laws of physics" in so doing---why does zinc cyanide expand under pressure ?

I don't think it defies the laws of physics. This looks like the usual journalists' hype. From what I read, it expands along one dimension. This would enable the material to respond to the pressure increase by reducing its overall volume (in accordance with "the laws of physics", but at the same time as extending itself along one axis.

But I'm open to correction, as I didn't now anything about the phenomenon until you alerted me to it.

exchemist:
From what I understood from what I read, the zinc cyanide expands in volume, not along one dimension(as in the zinc dicyanoaurate mentioned by PhDemon above).
Then, their reference to drying as part of industrial production process seems to support the idea that the expansion in volume is due to liquids being forced into the zinc cyanide making it sponge like. Which seems to be it's main value.

Yeh, me too: I'm open to correction;
and actually want it if/when I'm wrong.

Well bugger me! (figuratively speaking, of course.)

It seems to me the key passage in the paper is this one: "...While an increase in volume with pressure is counterintuitive, the resulting new phases contain large fluid-filled pores, such that the combined solid + fluid volume is reduced and the inefficiencies in space filling by the interpenetrated parent phase are eliminated."

So it indeed does not disobey the laws of physics, because it becomes an open structure penetrated by the fluid used to apply the pressure. It seems that this that allows the new structure to occupy less space overall than the fluid + solid starting point.

Interesting reading
interesting approach
I like that they listed their failures as well(different materials and different pressures...).

Don't some larger organic compounds also expand when put under pressure? Mostly because pressure increases heat or friction, not that they form a crystal. (only small molecules do this)

Originally Posted by Zwolver

Don't some larger organic compounds also expand when put under pressure? Mostly because pressure increases heat or friction, not that they form a crystal. (only small molecules do this)

Er, well, compressing a gas increases its temperature, but the volume change when applying pressure to a solid is pretty small and won't change the temperature much. I can't see how friction would come into it. Nothing is rubbing, surely?

Do you have examples of organic compounds that expand when compressed?