hydrogen atom in MOPAC

From: RUDOLF KIRALJ <KIRALJ : at : olimp.irb.hr>
Subject: hydrogen atom in MOPAC
Date: Wed, 2 Nov 1994 17:47:24 +0200 (IST)

 Hi Netters!
 The most trivial problem in calculating atomic structures is H atom. So
 the MOPAC 6.00 calculations gave 11.906 eV (MNDO), 11.396 eV (AM1) and
 13.073 eV (PM3) for hydrogen atom ionization potential. There is no
 difference in usign spin restricted or unrestricted hamiltonian. The
 experimental value is 13.595 eV. The differences between the experiment
 and calculations (roughly 1.7/2.2/0.5 for MNDO/AM1/PM3) are two or three
 orders of magnitude greater than experimental error. If in this case one
 have such difference, what about all other systems? Can somebody give
 appropriate explanation?
 Rudolf
 _________
 kiralj : at : olimp.irb.hr