<div dir="ltr"><div>Dear CP2K users and developers,<br><br></div>I am trying to calculate the energy difference between Au20 clusters (tetrahedral and planar geometries i.e. Et - Ep) on a graphene quantum dot substrate. After performing the initial tests with both BLYP functional and PBE functional with 60 Ry Rel_cutoff, I got the below results. <br><div><br></div> With BLYP functional With PBE functional:<br> Cutoff (Ry) Et - Ep (eV) <br> 300.000000 0.476312 300.000000 0.836360<br> 350.000000 0.478999 350.000000 0.838100<br> 400.000000 0.482285 400.000000 0.840190<br> 450.000000 0.484214 450.000000 0.840969<br> 500.000000 0.481904 500.000000 0.840789<br> 550.000000 0.485268 550.000000 0.841879<br> 600.000000 0.485097 600.000000 0.842565<br> 650.000000 0.485540 650.000000 0.842448<br> 700.000000 0.485891 700.000000 0.842935<br> 750.000000 0.485847 750.000000 0.842933<br> 800.000000 -1.372659 800.000000 -1.218138<br><br><div><br clear="all"></div><div><div><div><div dir="ltr"><span style="color:rgb(204,51,204)"><font color="#000000">Though it seems, from these results, that 550 Ry is sufficient for
calculating energy differences, I do have a doubt regarding the 800 Ry. Also, I want to let you know that all these calculations have been performed with 1 SCF cycle as mentioned in the tutorial and the absolute energies of each system got converged (with in 0.0001 Ha) only for 700 and 750 Ry.<br><br>If possible could you please let me know<br>(i) whether performing production runs with 550 Ry and 60 Ry for cutoff and Relcutoff is okay or not.<br><br>(ii) Calculations show PBE and BLYP need the same cutoff for a converged calculation. I have been repeatedly reading that BLYP needs more cutoff to get better calculations in the forum. Anything wrong or is it a special case?<br><br></font></span></div><div><span style="color:rgb(204,51,204)"><font color="#000000">(iii) I found that there is no change in the absolute energy (with 0.0001 Ha), for any Rel_cutoff between 40 to 90 Ry </font></span><span style="color:rgb(204,51,204)"><font color="#000000">(results not shown here). </font></span>I have tried with <span style="color:rgb(204,51,204)"><font color="#000000">cutoffs 350 Ry and 700 Ry. For both of these cutoffs absolute energies are not changing with relcutoff. Is it expected?<br><br></font></span></div><div><span style="color:rgb(204,51,204)"><font color="#000000">(iv) Can one expect a ~ 0.4 eV increment in the energy difference just by a change in the XC functional.<br><br></font></span></div><div dir="ltr"><span style="color:rgb(204,51,204)"><font color="#000000"> Input file is also attached for clarity.<br><br><br></font></span></div><div><span style="color:rgb(204,51,204)"><font color="#000000">Thanking you for your support,<br>Sincerely,<br>Sharma.<br></font></span></div><div dir="ltr"><span style="color:rgb(204,51,204)"><font color="#000000"><br></font></span></div><div><span style="color:rgb(204,51,204)"><font color="#000000">P.S. Sorry for the long mail.<br></font></span></div><div dir="ltr"><span style="color:rgb(204,51,204)"><font color="#000000"><br><br><br></font>********************************************************</span><br><font><b style="color:rgb(51,51,255)">Chaitanya Sharma,</b></font><br><b><span style="font-family:times new roman,serif">Prof. Pati'</span></b>s group,<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><span style="color:rgb(204,51,204)">*********************************************************</span><br></div></div>
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