H 1.0 1.03270 4.27032 2.11226 H 1.0 -0.26135 4.87344 1.64760 $end As GAMESS tells you, it is not possible to have singlet state (i.e. a multiplicity of 1) if you have an odd number of electrons. You need to tell GAMESS whether you want to change the multiplicity (for example, $contrl