From a chemical point of view, graphite is more stable than diamond because a more stable layered structure is formed between carbon atoms of graphite. At high temperature and high pressure, graphite can be transformed into diamond, so the stability of graphite is higher.
But in terms of physical properties, diamonds have higher hardness and wear resistance, so they are more popular in practical applications (such as jewelry, cutting tools, etc.). ).
Graphite is actually more stable than diamond in thermodynamics, that is to say, the reaction of diamond transforming into graphite will release heat.
But under high pressure, graphite can be spontaneously transformed into diamond, because in this reaction, the density of diamond is less than that of graphite, and its crystal structure cavity is relatively large. Lechatley's principle of chemical reaction reveals that when the reaction is carried out under high pressure, the reaction will be carried out in the direction of decompression. Since pV=nRT, the right side is unchanged, and increasing V can reduce P, then the reaction equilibrium moves towards diamond. In addition, diamond can be transformed into graphite under certain conditions (such as high temperature and high pressure), which shows that diamond can show higher stability in some cases.
Therefore, the choice of diamond or graphite as the material needs to be decided according to the specific application scenarios and conditions. In terms of chemical stability, graphite is better; In terms of physical properties, diamonds are better.