The $U{O}_6^{(6-)}$ anion

Another (difficult) case study example is the $U{O}_6^{(6-)}$ anion. The molecule is in squashed geometry (not fully octahedreal). Axial and equatorial bond distances are not equal.

The $U{O}_6^{(6-)}$ ground state

The ground state of $U{O}_6^{(6-)}$ converges fine, but not with the default DIIS and starting from screened bare nucleus. Rather one has to use the robust damping scheme. Try first the DAMPFC factor of 0.9:

pam  --noarch --get "DFCOEF=DFCOEF.UO6_6m_ground_1pass" --replace dampfactor=0.90 --inp=UO6_6minus.x2c.scf_damp.inp --mol=UO6.mol

(Files to download are UO6_6minus.x2c.scf_damp.inp and UO6.mol.)

Then, after we get the DFCOEF.UO6_6m_ground_1pass file, we decrease the damping level to 0.65. One could try also some lower value:

pam  --noarch --put "DFCOEF.UO6_6m_ground_1pass=DFCOEF" --get "DFCOEF=DFCOEF.UO6_6m_ground_2pass" --replace dampfactor=0.50 --inp=UO6_6minus.x2c.scf_damp.inp  --mol=UO6.mol

In this way we get converge molecular spinors saved in the DFCOEF.UO6_6m_ground_2pass file.

The $U{O}_6^{(5-)}$ anion

Now to the next state - the $U{O}_6^{(5-)}$ system. With $2p_{3/2}$ electron out of the U atom there is a difficult convergence. There are (at least) five siubsequent runs for that.

First run cca 500 iterations with the damping factor of 0.65 and with the shift of virtual spinors of +0.65. This goes very slowly. The pass two continues from pass one. Then pass three from previous pass up to pass 4, which has another 500 iteration. Damping factors of these passes were decreasing from 0.65 to 0.25. Finally, in pass 5 the convergence was reached with the default DIIS method:

pam  --noarch --put "DFCOEF.UO6_6m_ground_2pass=DFCOEF" --get "DFCOEF=DFCOEF.UO6_5m_2p3_1pass" --replace dampfactor=0.65 --inp=UO6_5m.x2c.scf_2p3_damp.inp --mol=UO6.mol
pam  --noarch --put "DFCOEF=DFCOEF.UO6_5m_2p3_1pass=DFCOEF" --get "DFCOEF=DFCOEF.UO6_5m_2p3_2pass" --replace dampfactor=0.55 --inp=UO6_5m.x2c.scf_2p3_damp.inp --mol=UO6.mol
pam  --noarch --put "DFCOEF=DFCOEF.UO6_5m_2p3_2pass=DFCOEF" --get "DFCOEF=DFCOEF.UO6_5m_2p3_3pass" --replace dampfactor=0.45 --inp=UO6_5m.x2c.scf_2p3_damp.inp --mol=UO6.mol
pam  --noarch --put "DFCOEF=DFCOEF.UO6_5m_2p3_3pass=DFCOEF" --get "DFCOEF=DFCOEF.UO6_5m_2p3_4pass" --replace dampfactor=0.25 --inp=UO6_5m.x2c.scf_2p3_damp.inp --mol=UO6.mol
pam  --noarch --put "DFCOEF=DFCOEF.UO6_5m_2p3_4pass=DFCOEF" --get "DFCOEF=DFCOEF.UO6_5m_2p3_diis_5pass" --inp=UO6_5m.x2c.scf_2p3.inp --mol=UO6.mol

(For downloading is the file UO6_5m.x2c.scf_2p3_damp.inp). Note that user may encounter difficulties when reproducing SCF convergence of this tutorial case.