Can diamond have a liquid state?

**stanton** · Nov11-09, 12:53 AM

In my lecture, my chemistry professor talked about Bonding in Solids. And he asked us whether diamond can melt(in other words, does diamond can have liquid state). And he did not know either.
And I was a bit confused. Because in my textbook, it says that Diamond is covalent network solid and Covalent network solid has huge melting point.

And I think Diamond can melt. Because if diamond cannot melt, the textbook should say 'with exception to diamond' something like that when putting diamond in Covalent network solid but there was no such word. And besides, they put diamond in category that claims the solids in that category has [melting point].

Can you tell what is right?

**Algr** · Nov11-09, 02:43 AM

Well, diamonds are carbon. What makes carbon a diamond instead of graphite or other forms is the arrangement of the atoms. But in a liquid, there is no fixed arrangement, so I don't think liquid carbon can be considered "diamond" or "graphite" or any other allotrope of carbon - it is just liquid carbon.

That may be more semantics then the chemistry that you were looking for. But I've found references to liquid carbon, so I suppose that might be what you are looking for.

Or are there multiple forms of liquid carbon?

**Borek** · Nov11-09, 05:56 AM

Originally Posted by Algr

Or are there multiple forms of liquid carbon?

No idea, but even if they are - none of them is diamond for the reasons you have elready listed.

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**Dadface** · Nov11-09, 06:56 AM

Originally Posted by Algr

Well, diamonds are carbon. What makes carbon a diamond instead of graphite or other forms is the arrangement of the atoms. But in a liquid, there is no fixed arrangement, so I don't think liquid carbon can be considered "diamond" or "graphite" or any other allotrope of carbon - it is just liquid carbon.

That may be more semantics then the chemistry that you were looking for. But I've found references to liquid carbon, so I suppose that might be what you are looking for.

Or are there multiple forms of liquid carbon?

Send your diamonds to me and I will do an experiment and send back the results.

**alxm** · Nov11-09, 12:57 PM

Diamond doesn't have a liquid state, because 'diamond' means 'carbon with 4 bonds' just as graphite means 'carbon with 3 bonds'. But a liquid is pretty much by definition a substance with an indefinite (or at least noninteger average) number of bonds, since they're continuously being broken and re-formed if it's in a liquid state.

Similarly you could compare to that there are several forms of water ice, corresponding to different bonding patterns. But there's only one liquid water.

**mgb_phys** · Nov11-09, 01:48 PM

So basically yes you could melt diamond but what you would have is liquid carbon since diamond is a particular solid form of carbon.

This is really linguistic hair splitting - it's like claiming you can't melt ice because then you would have liquid 'water' not liquid 'ice'.

**qraal** · Nov11-09, 03:10 PM

Diamond usually sublimes when heated, but at about 6000 K and a megabar or two it does form what can be called a liquid.

**mgb_phys** · Nov11-09, 04:29 PM

**stanton** · Nov12-09, 10:20 PM

Wow, thanks everybody! I must tell my proffessor about this. :)

**SrEstroncio** · Nov16-09, 07:30 PM

You can turn a diamond into CO2 using a liquid oxygen blowtorch.

**Borek** · Nov17-09, 03:25 AM

Originally Posted by SrEstroncio

You can turn a diamond into CO2 using a liquid oxygen blowtorch.

As far as I remember it is enough to heat them in the air. Not sure how high temperature is required, but nothing you will be not able to reach at home.

Don't try it with your Mom wedding ring

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**mgb_phys** · Nov17-09, 01:54 PM

Originally Posted by Borek

As far as I remember it is enough to heat them in the air. Not sure how high temperature is required,

There's a quote I remember from my chemistry textbook, after calculating the heat of combustion of diamond it notes "for obvious reasons diamond is not generally used as fuel"