| 6:35:53 AM PDT - Wed, Oct 30th 2019 |
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Having not ran large graphene simulations myself, I can only give general SCF convergence suggestions. Some possible strategies for SCF convergence are conveniently listed on Orca Input Library and can be adapted for NWChem:
1) Use the quadratic convergence algorithm: cgmin (analogous to !NRSCF keyword in orca). Here's a testimonial for cgmin with metallic systems in NWChem.
2a) Run a preliminary HF calculation, and use those vectors to start DFT calculation (example code), and/or
2b) Run a preliminary calculation for a cationic, closed-shell system, and then read those vectors into your desired neutral, open-shell system (example code).
3) Use a finer grid
4) Use more DIIS Fock matrices (default 10, but Orca Input Library suggests that 15-40 may be necessary for open-shell systems).
5) Increase damping and number of damped cycles for DIIS (somewhat analogous to !TIGHTSCF keyword in Orca)
Example input to implement suggestions 3, 4, and 5:
dft
grid fine
convergence diis 20
convergence damp 90
convergence ncydp 30
end
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