Dear Cp2k forum, We are trying to run a graphene sheet with a Fe defect (containing 1 Fe atom and 4 N atoms, 155 atoms in total), using spin polarized Kohn-Sham (UKS). We managed to run fixed multiplicities of 1, 3 and 5 using the keywords UKS and MULTIPLICITY and the orbital transformation algorithm. However, we would like to let the multiplicity relax using RELAX_MULTIPLICITY keyword and we haven’t been able to make any energy calculation converge yet. We are using DIAGONALIZATION instead of OT, with ADDED_MOS 500 and a Fermi-Dirac smearing with temperature 300 K. As of now we succeded to get convergence for DIAGONALIZATION – using the standard algorithm – (I) without UKS, (II) with UKS and a fixed MULTIPLICITY of 1, and (III) with UKS and RELAX_MULTIPLICITY starting from a multiplicity of 1 (but, however large the RELAX_MULTIPLICITY, we did not observe any switching of spin). Note that, even for the multiplicity 1, the SCF loop converges on a value higher than one found earlier in the loop (see below), and we therefore are not sure whether we can trust this. ############################################### SCF WAVEFUNCTION OPTIMIZATION Step Update method Time Convergence Total energy Change ------------------------------------------------------------------------------ 1 NoMix/Diag. 0.40E+00 1.0 0.94554597 -1011.7340994699 -1.01E+03 2 Broy./Diag. 0.40E+00 1.5 0.98949973 -984.4304450815 2.73E+01 3 Broy./Diag. 0.40E+00 1.5 1.00114938 -1018.8335907387 -3.44E+01 4 Broy./Diag. 0.40E+00 1.5 0.75169399 -1001.3444674373 1.75E+01 5 Broy./Diag. 0.40E+00 1.5 0.71210144 -1019.8272742272 -1.85E+01 6 Broy./Diag. 0.40E+00 1.4 0.91325270 -1013.4277794778 6.40E+00 7 Broy./Diag. 0.40E+00 1.4 0.50466440 -1029.6824961219 -1.63E+01 8 Broy./Diag. 0.40E+00 1.5 0.33674220 -1021.0650257790 8.62E+00 ... 40 Broy./Diag. 0.40E+00 1.4 0.00002151 -1017.3149228922 1.08E-04 41 Broy./Diag. 0.40E+00 1.4 0.00001546 -1017.3151997206 -2.77E-04 42 Broy./Diag. 0.40E+00 1.4 0.00000072 -1017.3150173627 1.82E-04 *** SCF run converged in 42 steps *** ######################################################## The fixed multiplicity of 3 is very hard to converge (we only managed with specific parameters of Broyden mixing, after 500 iteration steps, and the total spin moment (Mulliken population analysis) was not consistent with the given multiplicity). The RELAX_MULTIPLICITY case, starting from multiplicity 3 or 11, never converges (we set it to 1e-5, but different values up to 0.5 don’t change anything). We tried Pulay mixing but we got an error of bad conditioning, and Direct_p_mixing seems to worsen the convergence. We also tried using the method OT instead of STANDARD, with CG minimizer or DIIS (as done in a test case with O2), and in all cases it never converged and the OT eigensolver never converged at each step. Does anyone can suggest other parameters/methods to use or point out if there is a mistake in our simulations? We attach here a typical input file. Thank you very much, Sincerely, Laura -- You received this message because you are subscribed to the Google Groups "cp2k" group. To unsubscribe from this group and stop receiving emails from it, send an email to <a href="mailto:cp2k+unsubscribe@googlegroups.com">cp2k+unsubscribe@googlegroups.com</a>. To view this discussion on the web visit <a href="https://groups.google.com/d/msgid/cp2k/9a17d7d2-a92d-4b44-b689-c06a7ede197an%40googlegroups.com?utm_medium=email&utm_source=footer">https://groups.google.com/d/msgid/cp2k/9a17d7d2-a92d-4b44-b689-c06a7ede197an%40googlegroups.com</a>.