Dear all,

I want to calculate the singlet and triplet excited states of CH3I using EOM-EE-CCSD method. The results are so weird that I cannot explain.

Here is my input.

$molecule

0 1

H 0.7515158257 -0.6022789095 -1.8859686281

C 0.0000275280 -0.0000480643 -1.3297166588

H 0.1457682315 0.9524366931 -1.8856497472

H -0.8975405428 -0.3496077564 -1.8858774957

I -0.0000005683 0.0000001805 0.1707858230

$end

$rem

INPUT_BOHR FALSE

METHOD eom-ccsd

BASIS def2-tzvp

EE_SINGLETS [2]

EE_TRIPLETS [2]

CC_SYMMETRY FALSE

CC_MEMORY 2500

MEM_TOTAL 4000

$end

I used the geometry I got from Molpro, and the same basis set. Firstly, the Hartree-Fock energy I got from Molpro is -334 a.u., but q-chem returned me -2700 a.u., which I don't understand. Secondly, when I calculate the excited states, the excitation energy is negative for the first singlet and triplet excited state.

Does anyone have any sense what might be the reason for those two strange problems?

Thanks!