ethylene (only optimizing bond lengths; all angles, dihedrals frozen)
zmatrix angstroms
  c
  c       1 1.300
  h       1 1.100      2 120.0
  h       1 1.100      2 120.0      3 180.0
  h       2 1.100      1 120.0      3   0.0
  h       2 1.100      1 120.0      3 180.0
end
runtype start optimize
potential local
grid fine random
maxiterations 40
maxgeometries 10
econvergence 0.0000001
gconvergence 0.0001
mixing  0.350
maxstep 0.100
diis on
hessian 3
freeze 3 5 6 8 9 11 12
end
a-carbon (4,4;4,4)
a-carbon (4,4;4,4)
a-hydrogen (3,1;3,1)
a-hydrogen (3,1;3,1)
a-hydrogen (3,1;3,1)
a-hydrogen (3,1;3,1)
o-carbon (7111/411/1*)
o-carbon (7111/411/1*)
o-hydrogen (41/1*)
o-hydrogen (41/1*)
o-hydrogen (41/1*)
o-hydrogen (41/1*)
