Dear CP2K users, I apologise if a similar post has already been discussed but I only found one where a similar matter has been pointed out, that is <a href="http://groups.google.com/group/cp2k/browse_thread/thread/f1f4d594212348c1/c7f8b5c2f5a64789?lnk=gst&q=BS&pli=1">http://groups.google.com/group/cp2k/browse_thread/thread/f1f4d594212348c1/c7f8b5c2f5a64789?lnk=gst&q=BS&pli=1</a> , but this did not help. I am trying to compute the total energy of a single oxygen atom doing a spin-polarized energy calculation, however the Mulliken population analysis printed out in the end of the output file gives a total magnetic moment is 0, with both spin-up and spin down states having an occupation of 3 in the 2s and 2p orbitals, whereas one spin-state should be 4 and the other one 2, giving rise to a spin moment of 2. I have tried to fix this in the same way as explained in the post above, by using the section BS and biasing alpha and beta electrons in the chosen spin states but this didn`t fix it. Is this the correct way to do it but I am missing something or is there another way? Below is my relevant input file: &SUBSYS &CELL ABC 10 15 20 &END CELL &COORD SCALED O 0.5 0.5 0.5 &END COORD &KIND O BASIS_SET DZVP-MOLOPT-GTH-q6 POTENTIAL GTH-PBE-q6 &BS &ALPHA NEL 2 L 1 N 2 &END &BETA NEL -2 L 1 N 2 &END &END &END KIND &END SUBSYS Here there are the relevant parts of the output where first at the beginning the occupation has changed according to what specified, but at the end, after the total energy has been calculated, the mulliken population analysis shows again an occupation of 3 for both spin up and spin down states. This can ultimately result in wrong total energies, right? Atomic guess: The first density matrix is obtained in terms of atomic orbitals and electronic configurations assigned to each atomic kind Spin 1 Guess for atomic kind: O Electronic structure Total number of core electrons 2.00 Total number of valence electrons 8.00 Total number of electrons 10.00 Multiplicity not specified S [ 2.00] 2.00 P 6.00 After some lines... Spin 2 Guess for atomic kind: O Electronic structure Total number of core electrons 2.00 Total number of valence electrons 4.00 Total number of electrons 6.00 Multiplicity not specified S [ 2.00] 2.00 P 2.00 But finally, at the end of the calculation the wrong occupancies appear MULLIKEN POPULATION ANALYSIS # Atom Element Kind Atomic population (alpha,beta) Net charge Spin moment 1 O 1 3.000000 3.000000 -0.000000 -0.000000 # Total charge and spin 3.000000 3.000000 -0.000000 -0.000000 Any help would be kindly appreciated. Thanks.