ABINIT Discussion Forums

I am trying to calculate the Gamma frequencies of a given system. Everything went smooth for the ground state calculation but the ddk calculation is
complaining for no convergence after 600 steps!. How can I improve the convergence? Of course, no convergence, no possibility of getting the phonons.

Thansk and regards

-aldo.

Part of the input file looks like:

ndtset 3

iprcel 45

rfasr 2
#Ground state calculation
kptopt1 3
tolvrs1 1.0d-20
#Response Function calculation : d/dk
rfelfd2 2
rfdir2 1 1 1
nqpt2 1
qpt2 0.0 0.0 0.0
getwfk2 -1
kptopt2 3
iscf2 -3
tolwfr2 1.0d-22

#Response Function calculation : electric field perturbation and phonons
rfphon3 1
rfatpol3 1 8
rfelfd3 3
rfdir3 1 1 1
nqpt3 1
qpt3 0.0 0.0 0.0
getwfk3 -2
getddk3 -1
kptopt3 3
tolvrs3 1.0d-8

My standard answer in these cases is to check if the system is not becoming metallic, from an insulating ground state. So, you can try to run with occopt 7 and a very small tsmear, and ideally add a few more bands.

Check the end of the log for the "res" blocks which tell you how much each band is converged. It's possible that all but the last few are already fine...

Ciao

Matthieu

Dear Matthieu and all
I have same problem, when I trying in dataset 1 everything was well.
But when calculated dataset 2 ddk was no convergence after 200 steps.
My system was PbTiO3, once was shown piezoelectric properties.
Please help and comment me ! how can I going on.
see below my input files

occopt 7
tsmear 0.001

ndtset 3

# Set 1 : Initial self-consistent run

iscf1 5
kptopt1 1
tolvrs1 1.0d-18 #need excellent convergence of GS quantities for RF runs

# Set 2 : Calculate the ddk wf's - needed for piezoelectric tensor and
# Born effective charges in dataset 3

getwfk2 -1
iscf2 -3 #this option is needed for ddk
kptopt2 2 #use time-reversal symmetry only for k points
nqpt2 1 #one wave vector will be specified
qpt2 0 0 0 #need to specify gamma point
rfelfd2 2 #set for ddk wf's only
rfdir2 1 1 1 #full set of directions needed
tolwfr2 1.0d-20 #only wf convergence can be monitored here

# Set 3 : response-function calculations for all needed perturbations

getddk3 -1
getwfk3 -2
iscf3 5
kptopt3 2 #use time-reversal symmetry only for k points
nqpt3 1
qpt3 0 0 0
rfphon3 1 #do atomic displacement perturbation
rfatpol3 1 5 #do for all atoms
rfstrs3 3 #do strain perturbation
rfdir3 1 1 1 #the full set of directions is needed
tolvrs3 1.0d-10 #need reasonable convergence of 1st-order quantities


Best regards
Abdulmutta

Mutta wrote:Dear Matthieu and all
I have same problem,

I only have the same answer - see above...


matthieu

Following what Matt has suggested, please check convergence of the ground state.. is it converged? what about the
eigenvalues? you can check that and see if there is anything weird in one of them, which of course, it is easy to solve
by increasing a bit the number of bands.. what is the obtained gap after selfconsistency?

Hi all,

Why would the system become metallic? Besides, at the end of the calculation, all band occupancies are still integer and the material is still an insulator.

So occopt=7 is just used to help the algorithm find the minimum by lifting some constraints imposed with occopt=1?

Thanks

Boris

the GS is still insulating (as it should be), but the perturbation can break this an try to change occupations. If you impose occopt 1 this is impossible and the ddk may not converge. Adding unoccupied states would be an intermediate solution, but not always enough.

M.

Hi Users,

I am a new abinit user and I want to calculate the frozen phonon by Abinit at the Gamma point,
I used the tutorial but I did not know how to exploit it,
Thanks in advance.