<div dir="ltr">Hello Sir,<div>The units are in mRy. I tried with halving and doubling the F-D smearing value and the energy difference remains same (0.06mRy/atom) using largest k-point sampling. Can I rely on this F-D smearing (0.00184) results now ? I am also doing a convergent test on MV smearing with the largest k-point sampling.</div><div><br></div><div>Kind Regards</div><div><br></div><div>Paresh</div><div><br></div><div><span style="font-size:16px;background-color:rgb(0,0,0)"><font color="#000000"><br></font></span></div><div><br></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Wed, Jul 1, 2015 at 8:18 PM, Nicola Marzari <span dir="ltr"><<a href="mailto:nicola.marzari@epfl.ch" target="_blank">nicola.marzari@epfl.ch</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><br>
Hi Paresh,<br>
<br>
<br>
all good - but are you sure the units are mRy? A difference of<br>
0.06 mRy /atom is super small (11604K=1eV), so we are talking about<br>
10K difference, lost in the noise of the errors of approximate functionals,<br>
entropic effects, etc...<br>
<br>
Anyhow, if you want the computational "truth" you could try halving or<br>
doubling the fermi-dirac smearing (or m-v, or m-p), using the largest<br>
sampling,<br>
and see if you get the same number.<br>
<br>
nicola<br>
<span class=""><br>
<br>
On 01/07/2015 21:15, paresh rout wrote:<br>
> Sorry sir in the previous plot the energy difference was not per atom.<br>
> So here I am attaching the Corrected plot. My system contains 20 atom.<br>
><br>
> On Wed, Jul 1, 2015 at 6:09 PM, paresh rout <<a href="mailto:paresh.rout88@gmail.com">paresh.rout88@gmail.com</a><br>
</span><span class="">> <mailto:<a href="mailto:paresh.rout88@gmail.com">paresh.rout88@gmail.com</a>>> wrote:<br>
><br>
> Thank you very much sir. That was a very helpful reply. Now I<br>
> understand smearing. Just one more query, I did a convergence test<br>
> with k-point sampling by fixing the F-D smearing value to 0.00184<br>
> and the energy difference between C-type and G-type seems to be<br>
> converged (I have attached the convergent test plot). If I<br>
> understand your explanation correctly then this result should also<br>
> be reliable. Please let me know if I am wrong.<br>
><br>
> I will also do the convergent test with M-V(0.01) and the second<br>
> solution that you have suggested.<br>
> (The K-points grids are 8 8 6 , 10 10 8, 12 12 10, 14 14 12,<br>
> previously I was using 8 8 6)<br>
><br>
> Kind Regards<br>
> Paresh Chandra Rout<br>
> Research Scholar<br>
> INDIAN INSTITUTE OF SCIENCE EDUCATION AND RESEARCH, BHOPAL<br>
><br>
><br>
> On Wed, Jul 1, 2015 at 12:56 PM, Nicola Marzari<br>
</span><div><div class="h5">> <<a href="mailto:nicola.marzari@epfl.ch">nicola.marzari@epfl.ch</a> <mailto:<a href="mailto:nicola.marzari@epfl.ch">nicola.marzari@epfl.ch</a>>> wrote:<br>
><br>
><br>
><br>
> Dear Paresh,<br>
><br>
><br>
> maybe this is easier to follow:<br>
> <a href="http://theossrv1.epfl.ch/Main/ElectronicTemperature" rel="noreferrer" target="_blank">http://theossrv1.epfl.ch/Main/ElectronicTemperature</a><br>
><br>
> The main concept is that with very small smearing you need *a<br>
> lot* of<br>
> k-points<br>
> to perform the correct Brillouin zone integrations - so with a<br>
> 0.00184<br>
> smearing<br>
> you have a *large* error due to insufficient sampling, not a<br>
> small error.<br>
><br>
> Solution 1 - if you do not want to think, ever, in your life,<br>
> use 0.01<br>
> Ry of m-v<br>
> or m-v smearing, and increase the k-point sampling until the<br>
> difference<br>
> in energy<br>
> between G and C type is converged.<br>
><br>
> Solution 2 - plot the energy difference between G and C as a<br>
> function of<br>
> smearing,<br>
> for m-v smearing of 0.005, 0.010, 0.015, 0.020, 0.025, and with<br>
> at least<br>
> 3 or<br>
> 4 k-point sampling. Use the discussion from<br>
> <a href="http://theossrv1.epfl.ch/Main/ElectronicTemperature" rel="noreferrer" target="_blank">http://theossrv1.epfl.ch/Main/ElectronicTemperature</a><br>
> to understand what to do.<br>
><br>
> nicola<br>
><br>
><br>
><br>
> On 30/06/2015 17:07, paresh rout wrote:<br>
> > Dear all,<br>
> > I am dealing with a transition metal oxide compound (ABO3), Where I use<br>
> > cold smearing *m-v(0.02)* for geometry optimization and for total energy<br>
> > calculation I use *f-d (0.00184*) at the final optimized structure. I<br>
> > have calculated the total energy for various type of magnetic ordering<br>
> > like (G-type, C-type). The total energy (SCF) for G-type and C-type are<br>
> > in reverse ordering for different smearing technique (*G-type is the<br>
> > ground state for* *MV smearing and C-type is the ground state for FD*).<br>
> > But when I reduced the value of degauss of *MV to 0.008 *I got the same<br>
> > ordering as FD.<br>
> > I am very confused about the smearing technique . I have also read Prof.<br>
> > Nicola's thesis about smearing but there I did not get rid of my<br>
> > confusion also I did not find about FD technique . Can anybody kindly<br>
> > tell me about the right smearing technique which I can use for the spin<br>
> > polarized calculation ? Any reply would be highly appreciated.<br>
> ><br>
> ><br>
> > Kind Regards<br>
> > Paresh Chandra Rout<br>
> > Research Scholar<br>
> > INDIAN INSTITUTE OF SCIENCE EDUCATION AND RESEARCH, BHOPAL<br>
> ><br>
> ><br>
> ><br>
> > _______________________________________________<br>
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> --<br>
><br>
> ----------------------------------------------------------------------<br>
> Prof Nicola Marzari, Chair of Theory and Simulation of<br>
> Materials, EPFL<br>
> Director, National Centre for Competence in Research NCCR<br>
> MARVEL, EPFL<br>
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<br>
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Director, National Centre for Competence in Research NCCR MARVEL, EPFL<br>
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