# What is the melting point of diamond?

Textbooks and the online reference differ about this and there are more than two answers.

• Some additional information can be found here and the links within. – Nicolau Saker Neto Feb 20 '14 at 12:44
• melting point of diamond is 3823K – user10066 Nov 29 '14 at 7:26
• I wish this question would include a question … – Jan Oct 22 '17 at 3:18
• Liquid diamond certainly sounds cool. It even glows! – Volker Siegel Mar 24 '19 at 12:03

## 1 Answer

Diamond (carbon) does not melt at 1 atm. It sublimes to vapor.

Using carbon's theoretical phase diagram below (from Wikimedia), "liquid diamond" could be achieved at about 10 GPa (99 thousand atmospheres) and 5000 K (4700 °C).

Edit:

In fact, heating up diamonds at 1 atm turns them into graphite first. Only further heating would cause sublimation, as expected by observing the phase diagram. Here's a video:

http://www.youtube.com/watch?v=7L7BV3IBfFA

• It is 3783 K in reference books – user3286264 Feb 19 '14 at 15:01
• Note that if heating it in the atmosphere, it will burn to carbon dioxide much before it sublimates to vapour carbon. HEATING DIAMONDS IS A BAD IDEA! – Gimelist Nov 29 '14 at 8:11
• While I understand that the phase diagram you're using is mainly focused on the high temperature and pressure region, I can't help but feel that the boundaries of the metastable region could use some fine-tuning. Taken literally, it seems to be claiming that diamond isn't (meta)stable at room temperature and pressure(!). (Apparently, the actual thermal stability limit of diamond at low pressure is about 2000 K.) – Ilmari Karonen Feb 23 '16 at 19:29
• Definition (wikipedia): Sublimation - is the phase transition of a substance directly from the solid to the gas phase without passing through the intermediate liquid phase. – rtfminc May 23 '17 at 4:30
• Minor point: The quoted temperature conversion is mathematically correct, but in all probability no more than two digits are significant. Thus $5000 K=4700°C$. – Oscar Lanzi Oct 22 '17 at 10:01