[Pw_forum] The question about difference between diamond and graphite

[martins at if.uff.br]

Dear Alexander,

Unfortunately, I can't find your attached figure. Anyway, I'd like to  
make a comment. First, my question is: What did you compare? The total  
energies of diamond and graphite? If so, in my guess this procedure is  
wrong: you have to compare the formation energy of both compounds. For  
the diamond, the formation energy, E_for, would be:

E_for = E_tot(diamond) - 2*E_tot(single C atom, isolated)

In the above expression, I'm assuming that for the diamond calculation  
you used a 2-atom unitary cell. Again, FOR ME make sense only the  
comparison between the formation energies. If you did this, disregard  
my comment (but in you e-mail you mentioned "energy difference".)

Cheers,

Adriano

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Adriano de Souza Martins
Professor Adjunto III
Departamento de Física - ICEx
Polo Universitário de Volta Redonda
Universidade Federal Fluminense - Brazil
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