Dear Peter Blaha Sir,<div><br></div><div> Indeed by increasing number of K points we got the convergence. Sir I have now some basic queries on this topic. You have said that </div><div> "sometimes you cannot reach (easily) arbitrary convergence"</div>
<div>why in some cases we can not reach convergence up to our desired limit?...is it the limitation of DFT?....or it means that the feasibility of the solution is only up to the achieved convergence?</div><div><br></div><div>
Thanking you,</div><div>with best regards,<br><br><div class="gmail_quote">On Wed, Jul 6, 2011 at 6:13 PM, Peter Blaha <span dir="ltr"><<a href="mailto:pblaha@theochem.tuwien.ac.at">pblaha@theochem.tuwien.ac.at</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">For just 3 atoms/cell (and metallid ??) 1000 or 5000 k are still not much.<br>
Better k-mesh should improve convergence.<br>
<br>
And sometimes you cannot reach (easily) arbitrary convergence. What about E-tot, ... ?<br>
<br>
<br>
Am 06.07.2011 07:48, schrieb Shamik Chakrabarti:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div><div></div><div class="h5">
Dear wien2k users,<br>
<br>
We have done volume optimization of a structure having space group no. 225 (Fm3m) and 3 inequivalent atoms per unit cell. We have taken the least energy lattice parameters for<br>
spin polarized SCF calculations. However, the last calculation (spin polarized SCF) has not been converging at all. We have set the convergence criteria of charge to 0.0001and it<br>
reached up to 0.006. After that its is fluctuating sinusoidally at this value (even at around 400th iteration). We have also tried using the fallowing steps, such as<br>
<br>
1. increasing the RmaxKmax value from 7 to 9<br>
<br>
2. changing mixer values ranging from 0.01 to 0.3 (using MSEC mixing scheme...wien2k 10)<br>
<br>
3. increasing the K-points from 1000 to 5000<br>
<br>
but unfortunately we haven't got the desired convergence yet. Therefore, it is very helpful for us to have a suggestion for this problem.<br>
<br>
--<br>
Shamik Chakrabarti<br>
Research Scholar<br>
Dept. of Physics & Meteorology<br>
Material Processing & Solid State Ionics Lab<br>
IIT Kharagpur<br>
Kharagpur 721302<br>
INDIA<br>
<br>
<br>
<br></div></div>
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</blockquote>
<br>
-- <br>
<br>
P.Blaha<br>
------------------------------<u></u>------------------------------<u></u>--------------<br>
Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna<br>
Phone: +43-1-58801-15671 FAX: +43-1-58801-15698<br>
Email: <a href="mailto:blaha@theochem.tuwien.ac.at" target="_blank">blaha@theochem.tuwien.ac.at</a> WWW: <a href="http://info.tuwien.ac.at/theochem/" target="_blank">http://info.tuwien.ac.at/<u></u>theochem/</a><br>
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</blockquote></div><br><br clear="all"><br>-- <br>Shamik Chakrabarti<br>Research Scholar<br>Dept. of Physics & Meteorology<br>Material Processing & Solid State Ionics Lab<br>IIT Kharagpur<br>Kharagpur 721302<br>INDIA<br>
</div>