Hi Everyone,
I have a question regarding SCF convergence using PBE0. I am trying to
run an SCF calculation for a system (no metal) but cannot converge it.
The calculation runs infinite time with the message that convergence
is achieved in 2 or 3 iterations several times., like below:
----------------------------------------------
highest occupied, lowest unoccupied level (ev): -4.2577 -2.5888
! total energy = -261.58720112 Ry
estimated scf accuracy < 0.00000373 Ry
convergence has been achieved in 1 iterations
Using ACE for calculation of exact exchange
ACE projected onto 60 (nbndproj) and applied to 60 (nbnd) bands
BEWARE: negative dexx: -0.671E-01
total energy = -261.52011068 Ry
Harris-Foulkes estimate = -261.52011419 Ry
est. exchange err (dexx) = 0.06709044 Ry
- averaged Fock potential = 33.05795250 Ry
+ Fock energy (ACE) = -16.49568794 Ry
EXX: now go back to refine exchange calculation
total cpu time spent up to now is 73072.0 secs
---------------------------------------------------------------------------
However, the EXX is not converging whatever number of interactions I
run. The output prints these two lines at the end and terminates.
------------------------------------------
EXX: now go back to refine exchange calculation
EXX convergence NOT achieved after 150 iterations: stopping
----------------------------------------------
The geometry is fine and easily converges with PBE.
Can anyone suggest a way to converge this calculation? Which keywords
I can alter to smooth the convergence? Any advice on this will be
highly appreciated.
--
Rameswar Bhattacharjee
Department of Chemistry
Georgetown University
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