1. 
   hartree
   (E_h) Compare with atomic unit. The atomic unit of energy, equal to 4.359 743 81 × 10^-18 J ± 0.000 000 34 × 10^-18 J [1998 CODATA values].
   Found op http://antoine.frostburg.edu/chem/senese/101/glossary/h.shtml
   
   
2. 
   Hartree
   The hartree energy is approximately the electric potential energy of the hydrogen atom in its ground state and, by the virial theorem, approximately twice its ionization energy; the relationships are not exact because of the finite mass of the nucleus of the hydrogen atom and relativistic correctio...
   Found op http://en.wikipedia.org/wiki/Hartree
   
   

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