<div dir="ltr">Hi, everyone:<div><br></div><div>I have been doing a SO magnetic calculation on large systems (>200 atoms) using QE v5.1 (official release), and depending on number of pools, I experienced different convergence behaviors; my calculations have not been finished up to 100 iterations for both cases.</div><div>Although they are small, there are differences in total (absolute) magnetization and total energy.</div><div><span style="font-family:Menlo;font-size:11px"> </span><br></div><div><p style="margin:0px;font-size:11px;font-family:Menlo"><span style="font-family:arial;font-size:small">For example, I performed the same calculations using (1) 48 cores, 1 pool and (2) 96 cores, 2 pools.</span><br></p><p style="margin:0px;font-size:11px;font-family:Menlo"><span style="font-family:arial;font-size:small"><br></span></p><p style="margin:0px;font-size:11px;font-family:Menlo"><span style="font-family:arial;font-size:small">For (1) </span><span style="font-family:arial;font-size:small">48 cores, 1 pool, the part of results in final SCF step are as follows:</span></p><p style="margin:0px;font-size:11px;font-family:Menlo"><br></p><p style="margin:0px;font-size:11px;font-family:Menlo"> total energy = -286.41849742 Ry</p><p style="margin:0px;font-size:11px;font-family:Menlo"> Harris-Foulkes estimate = -286.41961400 Ry</p><p style="margin:0px;font-size:11px;font-family:Menlo"> estimated scf accuracy < 0.00021221 Ry</p><p style="margin:0px;font-size:11px;font-family:Menlo;min-height:13px"><br></p><p style="margin:0px;font-size:11px;font-family:Menlo"> total magnetization = 0.02 0.01 -0.01 Bohr mag/cell</p><p style="margin:0px;font-size:11px;font-family:Menlo"> absolute magnetization = 9.25 Bohr mag/cell</p><p style="margin:0px;font-size:11px;font-family:Menlo;min-height:13px"><br></p><p style="margin:0px;font-size:11px;font-family:Menlo"> End of self-consistent calculation</p><p style="margin:0px;font-size:11px;font-family:Menlo;min-height:13px"><br></p><p style="margin:0px;font-size:11px;font-family:Menlo">
</p><p style="margin:0px;font-size:11px;font-family:Menlo"> convergence NOT achieved after 100 iterations: stopping</p><p style="margin:0px;font-size:11px;font-family:Menlo"><br></p><p style="margin:0px;font-size:11px;font-family:Menlo"><span style="font-family:arial;font-size:small">For (2) 96</span><span style="font-family:arial;font-size:small"> cores, 2 pools, the part of results are as follows:</span><br></p><p style="margin:0px;font-size:11px;font-family:Menlo"><br></p><p style="margin:0px;font-size:11px;font-family:Menlo"> total energy = -286.41898856 Ry</p><p style="margin:0px;font-size:11px;font-family:Menlo"> Harris-Foulkes estimate = -286.41919445 Ry</p><p style="margin:0px;font-size:11px;font-family:Menlo"> estimated scf accuracy < 0.00035870 Ry</p><p style="margin:0px;font-size:11px;font-family:Menlo;min-height:13px"><br></p><p style="margin:0px;font-size:11px;font-family:Menlo"> total magnetization = 0.03 -0.03 0.00 Bohr mag/cell</p><p style="margin:0px;font-size:11px;font-family:Menlo"> absolute magnetization = 9.10 Bohr mag/cell</p><p style="margin:0px;font-size:11px;font-family:Menlo;min-height:13px"><br></p><p style="margin:0px;font-size:11px;font-family:Menlo"> End of self-consistent calculation</p><p style="margin:0px;font-size:11px;font-family:Menlo;min-height:13px"><br></p><p style="margin:0px;font-size:11px;font-family:Menlo">
</p><p style="margin:0px;font-size:11px;font-family:Menlo"> convergence NOT achieved after 100 iterations: stopping</p></div><div><br></div><div><br></div><div>For testing purposes, I also performed a calculation using example 11 with only modification of "<span style="font-family:Menlo;font-size:11px">starting_magnetization(1)=1.0" </span>in PW folder of QE v5.1.</div><div><br></div><div>In this case, difference is almost negligible, but there is clearly difference, e.g., total energy, "<span style="font-family:Menlo;font-size:11px">avg # of </span><span style="font-family:Menlo;font-size:11px;background-color:rgb(175,254,255)">iteration</span><span style="font-family:Menlo;font-size:11px">s",</span> and "<span style="font-family:Menlo;font-size:11px">polar coord.: r"</span>.</div><div>For example, I attach the results in iteration 1:</div><div><br></div><div>(1) 2 cores and 1 pool:</div><div><p style="margin:0px;font-size:11px;font-family:Menlo"> Self-consistent Calculation</p>
<p style="margin:0px;font-size:11px;font-family:Menlo;min-height:13px"><br></p>
<p style="margin:0px;font-size:11px;font-family:Menlo"> <span style="color:rgb(175,215,255);background-color:rgb(179,42,178)">iteration </span># 1 ecut= 45.00 Ry beta=0.70</p>
<p style="margin:0px;font-size:11px;font-family:Menlo"> Davidson diagonalization with overlap</p>
<p style="margin:0px;font-size:11px;font-family:Menlo"> ethr = 1.00E-02, avg # of iterations = 3.0</p>
<p style="margin:0px;font-size:11px;font-family:Menlo;min-height:13px"><br></p>
<p style="margin:0px;font-size:11px;font-family:Menlo"> ==============================================================================</p>
<p style="margin:0px;font-size:11px;font-family:Menlo"> atom number 1 relative position : 0.0000 0.0000 0.0000</p>
<p style="margin:0px;font-size:11px;font-family:Menlo"> charge : 6.365455</p>
<p style="margin:0px;font-size:11px;font-family:Menlo"> magnetization : 0.000000 -0.000000 4.270383</p>
<p style="margin:0px;font-size:11px;font-family:Menlo"> magnetization/charge: 0.000000 -0.000000 0.670868</p>
<p style="margin:0px;font-size:11px;font-family:Menlo"> polar coord.: r, theta, phi [deg] : 4.270383 0.000000 360.000000</p>
<p style="margin:0px;font-size:11px;font-family:Menlo;min-height:13px"><br></p>
<p style="margin:0px;font-size:11px;font-family:Menlo"> ==============================================================================</p>
<p style="margin:0px;font-size:11px;font-family:Menlo;min-height:13px"><br></p>
<p style="margin:0px;font-size:11px;font-family:Menlo"> total cpu time spent up to now is 4.1 secs</p>
<p style="margin:0px;font-size:11px;font-family:Menlo;min-height:13px"><br></p>
<p style="margin:0px;font-size:11px;font-family:Menlo"> total energy = -141.70484542 Ry</p>
<p style="margin:0px;font-size:11px;font-family:Menlo"> Harris-Foulkes estimate = -141.58797205 Ry</p>
<p style="margin:0px;font-size:11px;font-family:Menlo"> estimated scf accuracy < 0.30762031 Ry</p>
<p style="margin:0px;font-size:11px;font-family:Menlo;min-height:13px"><br></p>
<p style="margin:0px;font-size:11px;font-family:Menlo"> total magnetization = 0.00 -0.00 3.44 Bohr mag/cell</p>
<p style="margin:0px;font-size:11px;font-family:Menlo"> absolute magnetization = 3.44 Bohr mag/cell</p></div><div><br></div><div>(2) 4 cores and 2 pools</div><div><p style="margin:0px;font-size:11px;font-family:Menlo"> Self-consistent Calculation</p><p style="margin:0px;font-size:11px;font-family:Menlo;min-height:13px"><br></p><p style="margin:0px;font-size:11px;font-family:Menlo"> <span style="color:rgb(175,215,255);background-color:rgb(179,42,178)">iteration</span> # 1 ecut= 45.00 Ry beta=0.70</p><p style="margin:0px;font-size:11px;font-family:Menlo"> Davidson diagonalization with overlap</p><p style="margin:0px;font-size:11px;font-family:Menlo"> ethr = 1.00E-02, avg # of <span style="background-color:rgb(175,254,255)">iteration</span>s = 3.2</p><p style="margin:0px;font-size:11px;font-family:Menlo;min-height:13px"><br></p><p style="margin:0px;font-size:11px;font-family:Menlo"> ==============================================================================</p><p style="margin:0px;font-size:11px;font-family:Menlo"> atom number 1 relative position : 0.0000 0.0000 0.0000</p><p style="margin:0px;font-size:11px;font-family:Menlo"> charge : 6.365481</p><p style="margin:0px;font-size:11px;font-family:Menlo"> magnetization : 0.000000 -0.000000 4.270286</p><p style="margin:0px;font-size:11px;font-family:Menlo"> magnetization/charge: 0.000000 -0.000000 0.670850</p><p style="margin:0px;font-size:11px;font-family:Menlo"> polar coord.: r, theta, phi [deg] : 4.270286 0.000000 360.000000</p><p style="margin:0px;font-size:11px;font-family:Menlo;min-height:13px"><br></p><p style="margin:0px;font-size:11px;font-family:Menlo"> ==============================================================================</p><p style="margin:0px;font-size:11px;font-family:Menlo;min-height:13px"><br></p><p style="margin:0px;font-size:11px;font-family:Menlo"> total cpu time spent up to now is 4.0 secs</p><p style="margin:0px;font-size:11px;font-family:Menlo;min-height:13px"><br></p><p style="margin:0px;font-size:11px;font-family:Menlo"> total energy = -141.70484225 Ry</p><p style="margin:0px;font-size:11px;font-family:Menlo"> Harris-Foulkes estimate = -141.58795749 Ry</p><p style="margin:0px;font-size:11px;font-family:Menlo"> estimated scf accuracy < 0.30758887 Ry</p><p style="margin:0px;font-size:11px;font-family:Menlo;min-height:13px"><br></p><p style="margin:0px;font-size:11px;font-family:Menlo"> total magnetization = 0.00 0.00 3.44 Bohr mag/cell</p><p style="margin:0px;font-size:11px;font-family:Menlo">
</p><p style="margin:0px;font-size:11px;font-family:Menlo"> absolute magnetization = 3.44 Bohr mag/cell</p></div><div><br></div><div> </div><div>Is this just an inevitable numerical noise?</div><div><br></div><div>To my knowledge, it seems that just change of number of pools can't change the results at each SCF step.</div><div><br></div><div>Thanks in advance.</div><div><br></div><div>Regards.</div><div><br></div><div>H. Lee</div></div>