Dear Psi4 users and developers,

I did an HF calculation with O2 at 6-31g* basis set with psi4 and a different QC software. In both calculations, I turned off the symmetry and reorientation. I found the final energies as well as the orbital energies match extremely well (up to 5 decimal points). However, I found something I cannot understand when I look at their MO coefficients. For some of the MOs (e.g., 1st, E=-20.7553), the coefficients from the two molden files (one from each software) match perfectly after basis function re-ordering (since each software have their own convention of ordering basis functions), but for others (e.g., 8th, E=-0.5277) the coefficients are completely different (though the energies still match). But the same thing did not happen when I switch to a smaller basis set (i.e., 6-31g). I am wondering why this would happen?

The molden files of the 6-31g* basis set from two software are attached below. I appreciate any comments and help! Thanks!

Best,

Chenru

geo.molden.txt (57.5 KB) geo-tc.molden.txt (33.9 KB)