Hi, Flo, Thank you very much for your clarification. I was previously confused by the definition of overlap matrix, SMO. Now, I agree with you that the permutation operator is somehow problematic, and look forward to checking out your updated et_coupling codes. Hanning <div class="gmail_quote">On Thu, Nov 25, 2010 at 5:07 AM, flo <<a href="mailto:fsch...@pci.uzh.ch">fsch...@pci.uzh.ch</a>> wrote: <blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;"> Hi Hanning, thanks for looking into it. The index problem is solved in a bit a hidden way. The definition of SMO in cp2k is C_2^T S C_1 = SMO =S_21 note here as S, the overlap is symmetric it is valid S_21^T=(C_2^T S C_1)^T=C_1^T S C_2=S_12 furthermore the definition of the matrices rest_MO(1)=C_2^T V C_1=V_21 and rest_MO(2)=C_1^T V C_2=V_12 as b is computed as rest_MO(2) _kj * (S_21)^-1_kj this is equivalent to (V_12)_kj*(S_21)^-1_kj= (V_12)_kj * [(S_21)^-1]^T_jk = (V_12)_kj * (S_12)^-1_jk Took me as well a little while to understand this again. But yet I could not see (remember), why tttt (the kind of permutation operator) is in there. I had the formula out of the Loewdin paper P.-O. Löwdin, Phys. Rev. 97, 1474 (1955). The formulas there are not as straightforward as yours and it could be, that I derived a wrong formula for the determinant of minors in formula 51 in this paper. Trying to derive it again, I am almost sure that this permutation operator is wrong. I will change this in the code and submit the changes as soon as possible. Thank you very for having a look into this, <div><div></div><div class="h5"> Flo -- You received this message because you are subscribed to the Google Groups "cp2k" group. To post to this group, send email to <a href="mailto:cp...@googlegroups.com">cp...@googlegroups.com</a>. To unsubscribe from this group, send email to <a href="mailto:cp2k%2Bun...@googlegroups.com">cp2k+uns...@googlegroups.com</a>. For more options, visit this group at <a href="http://groups.google.com/group/cp2k?hl=en" target="_blank">http://groups.google.com/group/cp2k?hl=en</a>. </div></div></blockquote></div>