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<p><font size="2"><span style="font-size:10pt"><span style="font-size:12pt">Dear all,</span><br>
<span style="font-size:12pt"></span><br>
<span style="font-size:12pt">we would like to share with you some work of ours (see <a href="https://www.materialscloud.org/discover/sssp/" class="OWAAutoLink" id="LPlnk336885" previewremoved="true">https://www.materialscloud.org/discover/sssp/</a> and
<a href="https://www.nature.com/articles/s41524-018-0127-2" class="OWAAutoLink" id="LPlnk438581" previewremoved="true">
https://www.nature.com/articles/s41524-018-0127-2</a>) <br>
</span></span></font></p>
<p><font size="2"><span style="font-size:10pt"><span style="font-size:12pt">that we think it might
</span><span style="font-size:12pt">be useful for the user community of Quantum ESPRESSO.</span><br>
<span style="font-size:12pt"></span><br>
<span style="font-size:12pt">Over the last years, we have made a substantial effort on testing
</span><span style="font-size:12pt">pseudopotentials for precision and performance across several
</span><br>
<span style="font-size:12pt">open-source libraries that are available for QE.</span><br>
<span style="font-size:12pt">In summary, we have developed a pseudopotential testing protocol that
</span><span style="font-size:12pt">includes a verification part, based on the so-called delta-factor for
</span><br>
<span style="font-size:12pt">elemental solids, and an efficiency part, based on plane-wave cutoff
</span><span style="font-size:12pt">convergence tests for phonon frequencies, cohesive energies, pressures,
</span><br>
<span style="font-size:12pt">and band structures.</span><span style="font-size:12pt"> Adopting all these criteria, we have identified two optimal PBE
</span><span style="font-size:12pt"> pseudopotential libraries together with suggested
<br>
</span></span></font></p>
<p><font size="2"><span style="font-size:10pt"><span style="font-size:12pt">wavefunction cutoffs
</span><span style="font-size:12pt">for 85 elements of the periodic table, that we named "SSSP efficiency" and "</span><span style="font-size:12pt">SSSP precision" libraries
<br>
</span></span></font></p>
<p><font size="2"><span style="font-size:10pt"><span style="font-size:12pt">(where SSSP stands for standard solid-state
</span><span style="font-size:12pt">pseudopotential).</span><br>
<span style="font-size:12pt">The "SSSP efficiency"<u></u> library is designed for practical applications that
</span><span style="font-size:12pt">should remain affordable, and therefore pseudopotentials are</span><br>
<span style="font-size:12pt">chosen such that wavefunction cutoffs are as low as possible while
</span><span style="font-size:12pt">keeping the precision reasonable. For instance this library is well
</span><br>
<span style="font-size:12pt">suited for daily routine calculations or high-throughput materials screening.</span><br>
<span style="font-size:12pt">On the contrary, the "SSSP precision" library is more suited for
</span><span style="font-size:12pt">high-precision materials modelling as it contains pseudopotentials that
</span><br>
<span style="font-size:12pt">are the</span><span style="font-size:12pt"> closest to all-electron calculations, with less consideration on the
</span><span style="font-size:12pt">computational cost and the wavefunction cutoffs actually needed to
</span><br>
<span style="font-size:12pt">converge all relevant quantities.</span><br>
<span style="font-size:12pt"></span><br>
<span style="font-size:12pt">All the results and all the calculations inputs and outputs are
</span><span style="font-size:12pt">available on the Materials Cloud platform </span>
<br>
<span style="font-size:12pt"></span><a href="https://www.materialscloud.org/discover/sssp/" target="_blank" rel="noopener noreferrer" id="LPlnk900630" previewremoved="true"><span style="font-size:12pt">https://www.materialscloud.org/discover/sssp/</span></a><span style="font-size:12pt">.
We stress that, apart </span><span style="font-size:12pt">from the plug-and-play SSSP libraries,
<br>
</span></span></font></p>
<p><font size="2"><span style="font-size:10pt"><span style="font-size:12pt">our work provides also a useful database
</span><span style="font-size:12pt">of verification data and</span><span style="font-size:12pt"> convergence tests that facilitates the optimal choice
<br>
</span></span></font></p>
<p><font size="2"><span style="font-size:10pt"><span style="font-size:12pt">of pseudopotentials and
</span><span style="font-size:12pt">wavefunction cutoffs for custom applications. For example, some</span><span style="font-size:12pt"> physical properties may
<br>
</span></span></font></p>
<p><font size="2"><span style="font-size:10pt"><span style="font-size:12pt">be implemented only for some pseudopotential types or some
</span><span style="font-size:12pt">applications may require convergence of just a subset of the quantities
</span><br>
<span style="font-size:12pt">that we consider in the SSSP protocol. Indeed, by a look at our plots
</span><span style="font-size:12pt">and data, a user can quickly select the optimal
<br>
</span></span></font></p>
<p><font size="2"><span style="font-size:10pt"><span style="font-size:12pt">pseudopotential and wavefunction
</span><span style="font-size:12pt">cutoff tailored for the specific application.</span><br>
<span style="font-size:12pt"></span><br>
<span style="font-size:12pt">We underline that the SSSP libraries are a collection of pseudopotentials
</span><span style="font-size:12pt">generated by different authors. Please make an effort
<br>
</span></span></font></p>
<p><font size="2"><span style="font-size:10pt"><span style="font-size:12pt">to acknowledge all
</span><span style="font-size:12pt">original authors of libraries and methods if you use the SSSP results in your work,</span><span style="font-size:12pt"> see here
</span><br>
<span style="font-size:12pt"></span><a href="https://www.materialscloud.org/discover/sssp/table/efficiency#sssp-license" target="_blank" rel="noopener noreferrer" id="LPlnk10449" previewremoved="true"><span style="font-size:12pt">https://www.materialscloud.org/discover/sssp/table/efficiency#sssp-license</span></a><span style="font-size:12pt">
</span><br>
<span style="font-size:12pt">for a tentative acknowledgement list.</span><br>
<span style="font-size:12pt"></span><br>
<span style="font-size:12pt">If you want to know more about our work, it is discussed in a recent
</span><span style="font-size:12pt">article (<a href="https://www.nature.com/articles/s41524-018-0127-2" class="OWAAutoLink" id="LPlnk782717" previewremoved="true">https://www.nature.com/articles/s41524-018-0127-2</a>) that has just been published.</span><br>
<span style="font-size:12pt"></span></span></font></p>
<p><font size="2"><span style="font-size:10pt"><span style="font-size:12pt"><br>
</span></span></font></p>
<p><font size="2"><span style="font-size:10pt"><span style="font-size:12pt"><br>
</span></span></font></p>
<p><font size="2"><span style="font-size:10pt"><span style="font-size:12pt">Thank you,</span></span></font></p>
<p><br>
</p>
<p>The SSSP team</p>
<p>EPFL, Lausanne<br>
</p>
<p><br>
</p>
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