<div dir="ltr"><div><div>Dear Dr. Flo,<br><br>Thank you for the information. Among the points which you have raised, I indeed did the point 'C'. Sorry for not giving the sufficient information in previous post. Here in, I have attached the input file and the energy as a function of the optimization step, which shows it is pretty much converged. <br>
<br></div>So, do I need to switch off the " CENTER_COORDINATES" option after getting an optimized structure if I want to perform a single point energy calculation?<br><br>I have used a cutoff of 320 Ry and I also found that I cannot run all my systems (minimum 290 atoms and maximum 830 atoms with a cutoff of even 450 Ry) on the machines which are available for me. <br>
<br></div><div>Thanking you for your immediate response,<br></div><div>Sincerely,<br></div><div>Chaitanya Sharma.<br><br></div><div>P.S: Please let me know, if I need to give any more information to identify the exact problem.<br>
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<font><b style="color:rgb(51,51,255)">Chaitanya Sharma,</b></font><br><b><span style="font-family:times new roman,serif">Prof. Bala and Prof. Pati'</span></b>s groups,<br><span style="color:rgb(56,118,29)">Chemistry and Physics Materials unit</span>,<br>
<span style="color:rgb(255,0,0)">JNCASR</span>, BANGLORE,<br>Lab:: (080-2208) <span style="color:rgb(0,0,255)">2581, 2809</span><br><a href="https://sites.google.com/site/sharmasrkcyamijala/" target="_blank">https://sites.google.com/site/sharmasrkcyamijala/</a><br>
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<br><br><div class="gmail_quote">On Sat, Mar 8, 2014 at 12:34 PM, Florian Schiffmann <span dir="ltr"><<a href="mailto:flosch...@gmail.com" target="_blank">flosch...@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div dir="ltr">Dear Chaitanya,<br><br>usually if you have a properly converged structure and restart with the identical coordinates CP2K is very happy and will tell you it is converged. Without your input file with the exact details of your calculation it is fairly hard to tell what is going on. Nevertheless I will put some random guesses on.<br>
<br>a) your last structure wasn't perfectly optimized but reached the default step liimit of 200 steps<br>b) you use the default cutoff of 280 with elements like N/O/F. For these elements higher cutoffs (or smoothing) are needed to avoid grideffects (ripples) on your potential energy surface. If that's the case geometry optimizations will always have prolems to converge.<br>
c) you use a nonperiodic system and have the CENTER_COORDINATES option on. In combination with the cutoff problem this leaves you at a different position w.r.t. the grid points and thus with a different energy which can be further optimized.<br>
<br>I think b) and c) are most likely. Try a cutoff of 600 and see whether the problem still exists. <br>Of course higher cutoffs are expensive but it will give you a smooth PES and geometry optimizations will need much fewer steps and your ersults are converged wrt the auxillary basis.<br>
<br>One more comment to your a)<br>I think the bit about <i>"non-variational"-ness of the GPW method </i>you got from a prevous post from Jürg. He was talking about the convergence of the plane wave cutoff (better plane wave basis != lower energy). With fixed settings (basis,...) the GPW energy for a system is variational (lowest energy = best solution). Therefore forget about that point unless you try to converge your plane wave basis (which might be an idea, see b) :-)) <br>
<br>Cheers<br>Flo<br></div><div><div>
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