Fusionfire
Hazard to Others
Posts: 219
Registered: 8-7-2011
Member Is Offline
Mood: No Mood
|
|
Extended solids: your thoughts
Hello folks,
I came across this interesting document while trawling the web:
| Quote: |
Extended solids are high pressure phases whose properties are enhanced by the formation of high strength covalent bonds. |
What are your thoughts about it? It is certainly a fascinating prospect to hold polymeric CO, CO2, N2, etc. in your hand at RTP 
And the implications for energetics, armour, structural materials, etc. are huge.
Can such solids be made by imploding high explosives? Or will the subsequent release wave probably destroy them?
Attachment: XSolids Proposers Day.pdf (1.4MB)
This file has been downloaded 683 times
|
|
|
watson.fawkes
International Hazard
Posts: 2793
Registered: 16-8-2008
Member Is Offline
Mood: No Mood
|
|
Quote: Originally posted by Fusionfire  | | What are your thoughts about it? It is certainly a fascinating prospect to hold polymeric CO, CO2, N2, etc. in your hand at RTP |
Lest anybody who hasn't actually read the
referenced document be confused at this point, such materials do not yet exist. Also quoted from that document: | Quote: | | Inability to Stabilize at STP has seriously limited characterization of bulk properties and development for new materials |
This document is about offering funding for a research program. Maybe they can exist, maybe they can't.
|
|
|
Fusionfire
Hazard to Others
Posts: 219
Registered: 8-7-2011
Member Is Offline
Mood: No Mood
|
|
Actually production of extended solids has been done, on a microgram scale in a diamond anvil. They want to scale that up by at least 5 orders of
magnitude.
|
|
|
watson.fawkes
International Hazard
Posts: 2793
Registered: 16-8-2008
Member Is Offline
Mood: No Mood
|
|
Extended
solids that are stable at standard temperature and pressure do not, at this time, exist. The research program is to look for such materials.
|
|
|
Fusionfire
Hazard to Others
Posts: 219
Registered: 8-7-2011
Member Is Offline
Mood: No Mood
|
|
| Quote: Originally posted by watson.fawkes | | Quote: Originally posted by Fusionfire | | What are your thoughts about it? It is certainly a fascinating prospect to hold polymeric CO, CO2, N2, etc. in your hand at RTP |
Lest anybody who hasn't actually read the
referenced document be confused at this point, such materials do not yet exist. |
Yes they do exist. Some are only stable under extreme pressure. Others are stable at RTP. Diamond is arguably one of them - made under extreme
temperature & pressure but stable to behold at RTP.
| Quote: |
Also quoted from that document: | Quote: | | Inability to Stabilize at STP has seriously limited characterization of bulk properties and development for new materials |
This document is about offering funding for a research program. Maybe they can exist, maybe they can't. |
They do exist. Some at RTP, others in extreme TP.
|
|
|
Fusionfire
Hazard to Others
Posts: 219
Registered: 8-7-2011
Member Is Offline
Mood: No Mood
|
|
| Quote: Originally posted by watson.fawkes | | Extended
solids that are stable at standard temperature and pressure do not, at this time, exist. The research program is to look for such materials.
|
There are three aspects of design & manufacture of Extended Solids DARPA are interested in, but they are looking for "Synthesis and stabilization
of intermediates and extended solid phases."
They are looking at the end product, but also intermediates along the way to lessen the expenditure to make extended solids, and increase the yield to
practical scales.
|
|
|
watson.fawkes
International Hazard
Posts: 2793
Registered: 16-8-2008
Member Is Offline
Mood: No Mood
|
|
Diamond, however, does not require such pressures to be synthesized. Diamond can be grown epitaxially with the same gear that's used
for ordinary semiconductors. It's done at pressures that are in the realm of vacuum technology. Calling diamond an extended solid doesn't even fit the
definition you yourself quoted at the beginning of the thread, that identifies "extended solids" with "high pressure phases". It has high-strength
covalent bonds, yes, but the origin of those bonds doesn't require high pressure by any means.
I don't know of any of these "extended solids" that are stable at STP. That document you cited doesn't have any examples of them. The CO2 phases that
illustrate high-pressure phases, all of which do have different crystal and bond structures, do indeed fit the definition of extended solids, but they
aren't stable at STP. Got any others to propose?
|
|
|
blogfast25
International Hazard
Posts: 10562
Registered: 3-2-2008
Location: Neverland
Member Is Offline
Mood: No Mood
|
|
| Quote: Originally posted by Fusionfire |
Yes they do exist. Some are only stable under extreme pressure. Others are stable at RTP. Diamond is arguably one of them - made under extreme
temperature & pressure but stable to behold at RTP.
[snip]
They do exist. Some at RTP, others in extreme TP. |
Diamond is not 'arguably' an extended solid, whether produced under high pressure or not. Four entirely normal C-C sigma bonds keeping each C atom in
place make this a network-type material with extreme hardness. There are others of that type and none are extended solids.
Name me a few STP stable extended solids, please?
|
|
|
ScienceSquirrel
International Hazard
Posts: 1863
Registered: 18-6-2008
Location: Brittany
Member Is Offline
Mood: Dogs are pets but cats are little furry humans with four feet and self determination! 
|
|
One of their examples is stable at STP, that is the extended carbon disulphide and it has been made by other methods as well.
http://pubs.acs.org/doi/abs/10.1021/ja00150a026
|
|
|
arsphenamine
Hazard to Others
Posts: 236
Registered: 12-8-2010
Location: I smell horses, Maryland, USA
Member Is Offline
Mood: No Mood
|
|
| Quote: Originally posted by Fusionfire |
"Extended solids are high pressure phases whose properties are enhanced by the formation of high strength covalent bonds."
What are your thoughts about it? It is certainly a fascinating prospect to hold polymeric CO, CO2, N2, etc. in your hand at RTP |
Kinda leave N<sub>2</sub> out
of it since nitrogen is unusual in the Group 15 elements.
N<sub>4</sub>, for instance, exists barely long enough for detection, and it is
emphatically linear, not tetrahedral, and will not form sheets like its 2nd and 3rd row brethren.
180 kcal/mol ΔH<sub>f</sub> is a large energy expenditure for something that only sticks around for 1 μs.
|
|
|
Fusionfire
Hazard to Others
Posts: 219
Registered: 8-7-2011
Member Is Offline
Mood: No Mood
|
|
| Quote: Originally posted by watson.fawkes | Diamond, however, does not require such pressures to be synthesized. Diamond can be grown epitaxially with the same gear that's used
for ordinary semiconductors. It's done at pressures that are in the realm of vacuum technology. Calling diamond an extended solid doesn't even fit the
definition you yourself quoted at the beginning of the thread, that identifies "extended solids" with "high pressure phases". It has high-strength
covalent bonds, yes, but the origin of those bonds doesn't require high pressure by any means.
I don't know of any of these "extended solids" that are stable at STP. That document you cited doesn't have any examples of them. The CO2 phases that
illustrate high-pressure phases, all of which do have different crystal and bond structures, do indeed fit the definition of extended solids, but they
aren't stable at STP. Got any others to propose? |
Diamond is exactly the sort of extended solid they are talking about. At first our understanding was that it was made under high
temperatures and pressures. We then found less extreme reaction pathways to synthesise diamonds.
Polymeric CO, CO2, CN, N2, etc. in our current understanding can only be formed at pressures >300 GPa. But the research project is looking for
alternate pathways to make them more easily.
Anyway I don't see why we are debating these details. The facts which are plain are:
1) Polymeric forms of simple molecules can exist
2) Such forms under some circumstances can be stabilised to exist at RTP
3) Extended solids may have significant applications in energetics, armour and other fields
Debate the physical chemistry, the applications or the processes/technologies to get them. Please don't debate the semantics instead
Peace and sorry for any misunderstandings on my part.
|
|
|
Fusionfire
Hazard to Others
Posts: 219
Registered: 8-7-2011
Member Is Offline
Mood: No Mood
|
|
I will go out on a limb here and make the following statements, based on my understanding so far. Feel free to debate:
1) Subjecting previously unbonded molecules to high pressure does work on them, therefore their energy increases (pg 8 of the presentation)
2) If intermolecular bonds are formed, the reaction becomes exothermic in proportion to the bond energies and an "extended solid" is formed
3) Diassociation of the extended solid into its original phase (gas/liquid) requires some activation energy which may be supplied at room temperature
if the bonds formed in (2) are weak.
4) Whether the disassociation from the extended solid to initial phase is exothermic (applications in energetics) or endothermic (applications in
passive armour) depends on the difference between the work done to make the solid, and the heat produced in (2).
Work done = integral Pdv
5) The energy difference described in (4) is the only real "energy investment" that needs to be made (or absorbed, if endothermic) to make the
extended solid. Therefore the premise that lower energy pathways exist to make extended solids, is plausible.
All that seems to be just applications of basic physical principles. What I say now may seem a bit more hypothetical:
1) Referring to the Maxwell-Boltzmann distribution, extended solids are formed all the time especially in high temperature, high pressure gases of CO,
CO<sub>2</sub>, N<sub>2</sub>, etc. at the tail end of the distribution, when molecules happen to collide with each other
under the prerequisite circumstances.
2) Their persistencies in time is so short that they do not last long when they are formed, and decompose almost immediately afterwards.
My questions are:
1) Is there any way to observe the formation of extended solids for fleeting periods in high temperature, high pressure gases?
2) Are there any mistakes in my understanding?
3) We see in this paper:
http://www.nature.com/nmat/journal/v4/n3/abs/nmat1321.html
That extended CO explosively decomposes into CO<sub>2</sub> and glassy C. Is this the only known circumstance when:
2 CO -> CO<sub>2</sub> + C
with a large negative Gibbs free energy or are there other circumstances when CO may do so? What so special about the starting conditions for extended
CO that cause it to explosively decompose into CO<sub>2</sub> + C as a highly favoured reaction pathway?
|
|
|
blogfast25
International Hazard
Posts: 10562
Registered: 3-2-2008
Location: Neverland
Member Is Offline
Mood: No Mood
|
|
First it was: "Diamond is arguably one of them - made under extreme temperature & pressure but stable to behold at RTP", now it's "Diamond is
exactly the sort of extended solid they are talking about".
But you don't want to squabble about semantics, oh no!
|
|
|
Fusionfire
Hazard to Others
Posts: 219
Registered: 8-7-2011
Member Is Offline
Mood: No Mood
|
|
So exactly what do you want me to type, to put this discussion back on track?
|
|
|
arsphenamine
Hazard to Others
Posts: 236
Registered: 12-8-2010
Location: I smell horses, Maryland, USA
Member Is Offline
Mood: No Mood
|
|
The simple atom compounds
mentioned are perhaps too simple.
Let's speak about known extended solids first, then speculate from them.
We need to be careful about defining what an extended solid actually is. E.g., crystalline NaCl is realistically considered a near-infinite lattice
but the bonds are ionic thus easily sundered by a suitable electrolyte. Sounds extended to me, but lacking the desired properties.
Diamond, similarly, could be considered an extended compound, I suspect, and never mind how you get it.
BN, boron nitride has at least three basic covalent lattice structures, and few nanotubes as well. These are not simple BN monomers -- for some, the
molecule is exactly as large as the crystal.
So, while some first row elements actually form extended structures most do not seem to. Ab initio computations give suggestions as to which will or
won't.
2nd and 3rd row elements form extended covalent structures with little provocation, as any gloss of the last 15 years of phosphorus and arsenic
chemistry will tell you. [NB, don't do ab initio orbital computations on any but the simplest As, Sb, or Bi structures unless you have
institutional resources.]
Heterogeneous compounds are another matter. Your first look at a superconducting compound/lattice/WTF should make you blink. It may be exactly that
order of complexity with technologically useful extended solids.
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
