Hi<br />If possible, I would add on these questions as I had overlapping/similar ones.<br /><div><br /></div><div>A. SCF Convergence:</div><div><br /></div><div>a-What are the typical variables in cp2k that make sense to play around with, with trailing convergence? Are there some rule of thumbs that work well for values/ratios for ALPHA and NBROYDEN in the SCF/MIXING block? <br /></div><div><br /></div><div>b-I notice that i run into convergence issues with the SCCS solvation (and to an lesser extend the gCP correction, guess noise). Any tips for parameters for the SCCS block here?</div><div><br /></div><div>&SCCS on<br /><span style="white-space: pre;"> </span>&ANDREUSSI<br /><span style="white-space: pre;"> </span>RHO_MAX 0.001<br /><span style="white-space: pre;"> </span>RHO_MIN 0.0001 <br /></div><div>&END ANDREUSSI<br /> DIELECTRIC_CONSTANT 40<br /> EPS_SCF 1.0e-3<br /> EPS_SCCS 3.0E-6<br /> MAX_ITER 300<br /> &END SCCS<br /><br />c-As I come from non-periodic calcs: fermi smearing for convergence, what are acceptable temperatures to use? <br /></div><div><br /></div><div>B. Adding to the Fermi Smearing:</div><div><br /></div><div>Similar to molecular systems with strong static electron correlation (SEC) I looked into in the past, it might make sense for me to use FT-DFT as described in Grimme's FOD papers at smear temps of 20000K*%HFexchange + 5000K in geometry optimizations, freqs and single points to account for strong SEC effects. Is there anything in cp2k that would make FT_DFT behave differently/unexpectedly for these calcs as in programs like ORCA?<br /><br />C. Is there like a good practice reference I could look into for periodic calcs, similar to https://onlinelibrary.wiley.com/doi/10.1002/anie.202205735 for mostly non-periodic calcs?<br /><br />All the best</div><div class="gmail_quote"><div dir="auto" class="gmail_attr">usman ul muazzam schrieb am Freitag, 16. Mai 2025 um 13:14:43 UTC+2:<br/></div><blockquote class="gmail_quote" style="margin: 0 0 0 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;"><p>Dear CP2K Users
and Developers,</p>
<p>I am trying to model <strong>Ga and O adatom diffusion barriers</strong> on substrates like <strong>diamond and sapphire</strong> using CP2K (periodic DFT + NEB), and I have a few questions regarding best practices:</p>
<p><strong>1. k-point Sampling:</strong><br>Some CP2K publications seem to use <strong>only Gamma-point</strong>, even for periodic systems. In contrast, codes like Quantum ESPRESSO require k-point convergence for accuracy.</p>
<ul>
<li>
<p>Is k-point convergence generally <strong>not needed</strong> in CP2K.</p>
</li>
<li>
<p>When should one use explicit <strong>k-point grids</strong> in CP2K.</p>
</li>
</ul>
<p><strong>2. Slab Model Passivation:</strong><br>
In plane-wave codes, bottom surface passivation (e.g., with hydrogen) is common in slab models to avoid spurious states. But I rarely see this in CP2K-based surface studies.</p>
<ul>
<li>
<p>Is <strong>bottom-layer passivation not necessary</strong> in CP2K.</p></li>
</ul>
<p><strong>3. Convergence Parameters:</strong><br>
Is optimizing <strong>CUTOFF</strong> and <strong>REL_CUTOFF</strong> typically <strong>sufficient</strong> for accurate periodic DFT and NEB calculations in CP2K.</p>
<ul>
<li>
<p>Are other parameters like <strong>basis sets (as here we use Gaussian instead of plane wave)</strong> or <strong>grid levels</strong> also important to converge.</p>
</li>
<li>
<p>Any recommended references for CP2K convergence strategies.</p>
</li>
</ul>
<p>Any guidance or pointers to best practices would be greatly appreciated.</p><p><br></p><p>Best Regards,</p><p>Usman</p></blockquote></div>
<p></p>
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