First a disclaimer - I think this may be a uninformed question, so I apologize in advance What I would like to be able to do is understand fully the ADF output molecular orbitals in terms of the contributing bonding atomic orbitals, i.e. for H2 molecule, see that the MOs for a minimal basis set are: psi1 = c( |1sa> + |1sb>) psi2 = c( |1sa> - |1sb>) I have two questions remaining before I can really answer this question from the output. 1. Can I determine the relative signs of the added in basis orbitals? If I run H2, I get in the section "List of all MOs, ..." -7.161 2.00 1 A 50.00% 1 S -3.376 1.00 1 H 50.00% 1 S -3.376 1.00 2 H 2.472 0.00 2 A 50.00% 1 S -3.376 1.00 2 H 50.00% 1 S -3.376 1.00 1 H So, this is what I expect from above, except that the I've lost the negative sign on the LUMO orbitals, but I supposed that this was part of the design to not imply too much info., because with non s-type orbitals we have shape as well as phase, and we would need to worry about the location of the orbitals to see if the overlap is constructive or destructive. but, if I now run this with a double-zeta basis set, the output becomes: -9.087 2.00 1 A 50.68% 1 S -6.666 1.00 2 H 50.68% 1 S -6.666 1.00 1 H -1.928 0.00 2 A 55.88% 1 S -6.666 1.00 1 H 55.88% 1 S -6.666 1.00 2 H -5.88% 2 S 10.542 0.00 2 H -5.88% 2 S 10.542 0.00 1 H so we now have negative contributions. I guess then, question one is what is the significance of the negative percentage SFO contribution when it doesn't show the sign of the orbital that is added in for the linear combination? And this also brings up, how can I determine the antibonding/bonding nature of the linear combination of atomic orbitals? From the output section "SFO overlap matrix", I can tell if a linear combination is bonding/antibonding, but I need to know the signs of each SFO in the final MO. 2. I would also like to be able to be able to deconstruct the SFOs in terms of the basis functions. For example in the above DZ calculation, I see from the output of the create job that I have two orbitals of 1s symmetry from the section "Orbital Energies, per ..." Occup E (au) E (eV) Diff (eV) with prev. cycle ----- -------------------- ------ -------------------------- S 1 1.000 -0.24495278897385E+00 -6.666 3.69E-09 2 0.000 0.38741497816209E+00 10.542 so it seems that the two basis 1s functions have formed two linear combinations which are of course of s-type symmetry. My question is what the coefficients of each of the two basis functions in the orbitals is. The point is that I would like to know in the output of the actual density calculation what the SFOs that contribute to an MO look like, e.g. for the DZ calculation of H2 above, the output shows -5.8% of the LUMO from the create run, so I would like to know what exactly this means in terms of the basis functions. btw, this is where we run into my ignorance, because I'm not sure where the orthogonality of the HOMO/LUMO of the create run arises - if we just have 1s slater functions which have no nodes and are spherically symmetric, how is the overlap zero? Is the create-run LUMO formed something like: 1s(basis fn 1) - 1s(basis fn 2) to provide a sort of 2s function and yield the zero overlap? and in larger calculations, are the e.g. 3s basis functions which have no nodes combined to make an SFO which does? Anyway, just struggling to make sure I'm actually understanding what I'm doing from the ground up, I'd appreciate help for the first two questions about the format of the output (how to deconstruct MOs in terms of the linear combination of SFOs including signs, and the similiar problem with SFOs and basis functions). The last paragraph of questions is really just a signpost for my ignorance, but I'm not a computational chemist, so I hope that excuses me enough for someone to provide a useful comment or reference.