Dear Mehrdad Zamzamian
Please sign always your posts to the forum with name and scientific
affiliation, we appreciate it.
I suppose that the error is in the calculation of the single Fe atom.
You should calculate the formation energy with respect to the
reference energy of a Fe atom in its standard state, that is the bcc
crystal.
HTH
Giuseppe
Quoting mehrdad zamzamian <[email protected]>:
with regard
I want to calculate vacancy formation energy in Fe3C. I calculated the
following results by using these two pp:
Fe 55.84500 Fe.pbe-nd-rrkjus.UPF
C 12.01070 C.pbe-rrkjus.UPF
total energy of 64 atoms= -2860.35431865 Ry
total energy of 63 atoms (removing a Fe atom)= -2804.44525448 Ry
total energy of a single Fe atom= -55.45181620 Ry
using two ways i can calculate:
the first one) E(vacancy)= -2804.44525448 +(63/64)*2860.35431865
=11.21602794 Ry =152.60188965 eV!!!!!!
the second way) E(vacancy)= +2860.35431865-2804.44525448-55.45181620=
0.45724797 Ry =6.2211778211 eV!!!!!!
but in references, it must be ~1.61 eV ( and also i reached to this value
using MD simulation). what is wrong? Which calculation way is correct?
Thanks
GIUSEPPE MATTIOLI
CNR - ISTITUTO DI STRUTTURA DELLA MATERIA
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I-00015 - Monterotondo Scalo (RM)
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E-mail: <[email protected]>
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