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<div dir="ltr"><span class="x_elementToProof" style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)">Hello,</span>
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I've been using QE for several years and recently came across an interesting issue when try to converge certain large systems.</div>
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Attached is a link to an inputfile for a 216 atom system. With QE-6.8 (also tested on v6.3), the structure converges only if nosym=.f. and noinv=.f.. There are two symmetry operations found, the identity and inversion.
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Setting nosym=.t. causes the estimated scf accuracy to thrash around in the hundreds of thousands of Ry, while nosym=.f. allows strong convergence (1e-6 Ry) within 30 iterations.</div>
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Pseudopotentials are all pslibrary PBE. Below is a link to the inputfile and relevant parts of the scf output.</div>
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I would appreciate any advice for understanding what the heck is going on here.</div>
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-Frank Cerasoli</div>
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UC Davis Department of Chemistry<br>
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From the outputs:</div>
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With nosym=.f.</div>
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Program PWSCF v.6.8 starts on 4Apr2022 at 16:30:24<br>
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...</div>
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2 Sym. Ops., with inversion, found</div>
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...</div>
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iteration # 1 ecut= 41.00 Ry beta= 0.10</div>
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<div> total energy = -84091.83957606 Ry</div>
<div> estimated scf accuracy < 7.57588335 Ry</div>
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<span></span> iteration # 2 ecut= 41.00 Ry beta= 0.10
<div> total energy = -84090.73018546 Ry</div>
<span> estimated scf accuracy < 5.24675479 Ry</span><br>
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iteration # 3 ecut= 41.00 Ry beta= 0.10</div>
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<div> total energy = -84091.16546184 Ry</div>
estimated scf accuracy < 0.84010802 Ry</div>
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With nosym=.t.</div>
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Program PWSCF v.6.8 starts on 4Apr2022 at 18: 9:20</div>
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...<br>
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No symmetry found<br>
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...</div>
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iteration # 1 ecut= 41.00 Ry beta= 0.10</div>
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<div> total energy = -83948.30076200 Ry</div>
<div> estimated scf accuracy < 364559.66452101 Ry</div>
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<div> iteration # 2 ecut= 41.00 Ry beta= 0.10</div>
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<div> total energy = -84392.52517827 Ry</div>
<div> estimated scf accuracy < 209530.42525106 Ry</div>
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<div> iteration # 3 ecut= 41.00 Ry beta= 0.10</div>
...<span style="background-color:rgb(255,255,0)"></span><br>
<div> total energy = -85690.00953396 Ry</div>
<span> estimated scf accuracy < 338759.15202062 Ry</span></div>
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And the inputfile is here:</div>
<span class="x_elementToProof" style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)"><a href="https://drive.google.com/file/d/1jaF7drV996sg4ckxYunyHPpE79SRDdjZ/view?usp=sharing" data-auth="NotApplicable">https://drive.google.com/file/d/1jaF7drV996sg4ckxYunyHPpE79SRDdjZ/view?usp=sharing</a></span></div>
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