Thank you very much sir. That was a very helpful reply. Now I understand smearing. Just one more query, I did a convergence test with k-point sampling by fixing the F-D smearing value to 0.00184 and the energy difference between C-type and G-type seems to be converged (I have attached the convergent test plot). If I understand your explanation correctly then this result should also be reliable. Please let me know if I am wrong.
I will also do the convergent test with M-V(0.01) and the second solution that you have suggested. (The K-points grids are 8 8 6 , 10 10 8, 12 12 10, 14 14 12, previously I was using 8 8 6) Kind Regards Paresh Chandra Rout Research Scholar INDIAN INSTITUTE OF SCIENCE EDUCATION AND RESEARCH, BHOPAL On Wed, Jul 1, 2015 at 12:56 PM, Nicola Marzari <nicola.marz...@epfl.ch> wrote: > > > Dear Paresh, > > > maybe this is easier to follow: > http://theossrv1.epfl.ch/Main/ElectronicTemperature > > The main concept is that with very small smearing you need *a lot* of > k-points > to perform the correct Brillouin zone integrations - so with a 0.00184 > smearing > you have a *large* error due to insufficient sampling, not a small error. > > Solution 1 - if you do not want to think, ever, in your life, use 0.01 > Ry of m-v > or m-v smearing, and increase the k-point sampling until the difference > in energy > between G and C type is converged. > > Solution 2 - plot the energy difference between G and C as a function of > smearing, > for m-v smearing of 0.005, 0.010, 0.015, 0.020, 0.025, and with at least > 3 or > 4 k-point sampling. Use the discussion from > http://theossrv1.epfl.ch/Main/ElectronicTemperature > to understand what to do. > > nicola > > > > On 30/06/2015 17:07, paresh rout wrote: > > Dear all, > > I am dealing with a transition metal oxide compound (ABO3), Where I use > > cold smearing *m-v(0.02)* for geometry optimization and for total energy > > calculation I use *f-d (0.00184*) at the final optimized structure. I > > have calculated the total energy for various type of magnetic ordering > > like (G-type, C-type). The total energy (SCF) for G-type and C-type are > > in reverse ordering for different smearing technique (*G-type is the > > ground state for* *MV smearing and C-type is the ground state for FD*). > > But when I reduced the value of degauss of *MV to 0.008 *I got the same > > ordering as FD. > > I am very confused about the smearing technique . I have also read Prof. > > Nicola's thesis about smearing but there I did not get rid of my > > confusion also I did not find about FD technique . Can anybody kindly > > tell me about the right smearing technique which I can use for the spin > > polarized calculation ? Any reply would be highly appreciated. > > > > > > Kind Regards > > Paresh Chandra Rout > > Research Scholar > > INDIAN INSTITUTE OF SCIENCE EDUCATION AND RESEARCH, BHOPAL > > > > > > > > _______________________________________________ > > Pw_forum mailing list > > Pw_forum@pwscf.org > > http://pwscf.org/mailman/listinfo/pw_forum > > > > -- > > ---------------------------------------------------------------------- > Prof Nicola Marzari, Chair of Theory and Simulation of Materials, EPFL > Director, National Centre for Competence in Research NCCR MARVEL, EPFL > _______________________________________________ > Pw_forum mailing list > Pw_forum@pwscf.org > http://pwscf.org/mailman/listinfo/pw_forum >
Conv.pdf
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