Atomization energy

[Peter Wu]

Dear all:

      My goal is to get the atomization energy(with pseudo-
potential).
      But it  is very  different for the energy of atom.
      Is it the true atom total energy in the output file with atomic
guess.
      I can not get  the same energy for atom only calculation.
      eg: -54a.u. for Oxygen .     About -16a.u. for Oxygen in
H2O !
           And  Guess for atomic kind: O is  about -15 a.u.?
           Dose pseudo-potential  for atoms work ?
           How to get the atomization energy ? (use guess for atomic
kind ?)
 
Best regards     Peter