Dear Rencong,<br>
<br>
I had similar experiences when I use QE pw.x to relax structures under pressure and I want to follow this conversation. <br>
<br>
My experience is that, the behaviour and result of relaxation depend largely on the pesudopotential. <br>
<br>
It is also helpful to investigate the energy and pressure during the relaxation. <br>
<br>
In order for other experts to help you, could you please provide:<br>
(1) the pseudopotentials used in the calculation<br>
(2) the entire output file of pw.x, or at least the section contains the final coordinates? (search "End of BFGS" in the output file)<br>
(3) your name and affiliation (this is the rule of the mailing list)<br>
<br>
Best,<br>
Yunlong <br>
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<br>
<br>
<span>--<br>
Yunlong LIAN
ORCID : https://orcid.org/0000-0002-9474-2181
CSNS, Dongguan Neutron Science Center
Dongguan, Guangdong, P. R. China
连云龙
中国散裂中子源 中子科学部
A1-629 (内线 303)
中国广东省东莞市</span><br>
<blockquote name="replyContent" class="ReferenceQuote" style="padding-left:5px;margin-left:5px;border-left:#b6b6b6 2px solid;margin-right:0;">
-----Original Messages-----<br>
<b>From:</b><span id="rc_from">Amadeus <760158264@qq.com></span><br>
<b>Sent Time:</b><span id="rc_senttime">2021-05-25 15:22:02 (Tuesday)</span><br>
<b>To:</b> users <users@lists.quantum-espresso.org><br>
<b>Cc:</b> <br>
<b>Subject:</b> [QE-users] under pressure PbTaSe2 vc-relax calculation<br>
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<span style="font-size:14px;">Dear QE developer</span>
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<span style="font-size:14px;">I did the structural relaxation calculation for Pb at pressure of 3kbar， this is relax.in</span>
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<span style="font-size:14px;">&CONTROL</span>
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<span style="font-size:14px;"> prefix='PbTaSe2',</span>
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<span style="font-size:14px;"> calculation='vc-relax', pseudo_dir='../../', outdir='./tmp', verbosity='high',</span>
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<span style="font-size:14px;"> tprnfor=.true., tstress=.true., forc_conv_thr=1.0d-4, nstep=100,</span>
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<span style="font-size:14px;">/</span>
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<span style="font-size:14px;">&SYSTEM</span>
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<span style="font-size:14px;"> ibrav= 0, nat= 4, ntyp= 3, </span>
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<span style="font-size:14px;"> occupations = 'smearing', smearing = 'gauss', degauss = 1.0d-2,</span>
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<span style="font-size:14px;"> ecutwfc = 50, ecutrho = 500,</span>
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<span style="font-size:14px;">/</span>
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<span style="font-size:14px;">&ELECTRONS</span>
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<span style="font-size:14px;"> conv_thr = 1.0d-8</span>
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<span style="font-size:14px;"> mixing_beta = 0.7d0</span>
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<span style="font-size:14px;">/</span>
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<span style="font-size:14px;">&IONS</span>
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<span style="font-size:14px;">/</span>
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<span style="font-size:14px;">&CELL</span>
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<span style="font-size:14px;"> cell_dynamics = "bfgs"</span>
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<span style="font-size:14px;"> press = 2.70000e+00</span>
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<span style="font-size:14px;"> press_conv_thr =0.1</span>
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<span style="font-size:14px;">/</span>
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<span style="font-size:14px;">ATOMIC_SPECIES</span>
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<span style="font-size:14px;"> Ta 180.9479 Ta.UPF</span>
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<span style="font-size:14px;"> Pb 207.2 Pb.UPF</span>
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<span style="font-size:14px;"> Se 78.96 Se.UPF</span>
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<span style="font-size:14px;">CELL_PARAMETERS (angstrom)</span>
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<span style="font-size:14px;"> 3.4834700000 0.0000000000 0.0000000000</span>
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<span style="font-size:14px;"> -1.7417350000 3.0167735133 0.0000000000</span>
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<span style="font-size:14px;"> 0.0000000000 0.0000000000 9.4755300000</span>
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<span style="font-size:14px;">ATOMIC_POSITIONS (crystal)</span>
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<span style="font-size:14px;"> Pb 0.0000000000 0.0000000000 0.0000000000</span>
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<span style="font-size:14px;"> Se 0.0000000000 0.0000000000 0.3246710000</span>
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<span style="font-size:14px;"> Ta 0.3333330000 0.6666670000 0.5000000000</span>
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<span style="font-size:14px;"> Se 0.0000000000 0.0000000000 0.6753290000</span>
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<span style="font-size:14px;">K_POINTS {automatic}</span>
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<span style="font-size:14px;"> 15 15 5 0 0 0</span>
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<span style="font-size:14px;">In relax.in, press=3.0kbar. But after pw.x is done, relax.out show that total stress (Ry/bohr**3) (kbar) P=-0.83, and This is inconsistent with press=3. this is part of relax.out</span>
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<span style="font-size:14px;">[rencong@mu01 phonon]$ grep 'Computing stress (Cartesian axis) and pressure' -A 15 relax.out</span>
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....
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<span style="font-size:14px;"> Computing stress (Cartesian axis) and pressure</span>
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<span style="font-size:14px;"> total stress (Ry/bohr**3) (kbar) P= 2.93</span>
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<span style="font-size:14px;"> 0.00002030 -0.00000000 0.00000000 2.99 -0.00 0.00</span>
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<span style="font-size:14px;"> -0.00000000 0.00002030 -0.00000000 -0.00 2.99 -0.00</span>
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<span style="font-size:14px;"> -0.00000000 0.00000000 0.00001921 -0.00 0.00 2.83</span>
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<span style="font-size:14px;"> kinetic stress (kbar) 26877.23 0.00 0.00</span>
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<span style="font-size:14px;"> 0.00 26877.23 -0.00</span>
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<span style="font-size:14px;"> 0.00 0.00 26796.57</span>
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<span style="font-size:14px;"> local stress (kbar)-103340.53 0.03 0.00</span>
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<span style="font-size:14px;"> 0.03-103340.50 0.00</span>
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<span style="font-size:14px;"> 0.00 0.00 89394.48</span>
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<span style="font-size:14px;"> nonloc. stress (kbar) 7797.15 0.00 0.00</span>
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<span style="font-size:14px;">--</span>
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<span style="font-size:14px;"> Computing stress (Cartesian axis) and pressure</span>
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<span style="font-size:14px;"> total stress (Ry/bohr**3) (kbar) P= 2.96</span>
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<span style="font-size:14px;"> 0.00002009 -0.00000000 0.00000000 2.96 -0.00 0.00</span>
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<span style="font-size:14px;"> -0.00000000 0.00002009 -0.00000000 -0.00 2.96 -0.00</span>
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<span style="font-size:14px;"> 0.00000000 -0.00000000 0.00002028 0.00 -0.00 2.98</span>
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<span style="font-size:14px;"> kinetic stress (kbar) 26879.49 0.00 0.00</span>
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<span style="font-size:14px;"> 0.00 26879.49 -0.00</span>
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<span style="font-size:14px;"> 0.00 -0.00 26798.86</span>
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<span style="font-size:14px;"> local stress (kbar)-103299.75 0.03 0.00</span>
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<span style="font-size:14px;"> 0.03-103299.72 0.00</span>
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<span style="font-size:14px;"> 0.00 0.00 89348.84</span>
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<span style="font-size:14px;"> nonloc. stress (kbar) 7797.79 -0.00 0.00</span>
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<span style="font-size:14px;">--</span>
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<span style="font-size:14px;"> Computing stress (Cartesian axis) and pressure</span>
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<span style="font-size:14px;"><br>
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<span style="font-size:14px;"> total stress (Ry/bohr**3) (kbar) P= -0.83</span>
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<span style="font-size:14px;"> -0.00000653 -0.00000000 -0.00000000 -0.96 -0.00 -0.00</span>
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<span style="font-size:14px;"> 0.00000000 -0.00000653 0.00000000 0.00 -0.96 0.00</span>
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<span style="font-size:14px;"> 0.00000000 0.00000000 -0.00000384 0.00 0.00 -0.56</span>
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<span style="font-size:14px;"> kinetic stress (kbar) 26883.07 0.00 -0.00</span>
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<span style="font-size:14px;"> 0.00 26883.07 -0.00</span>
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<span style="font-size:14px;"> -0.00 -0.00 26802.38</span>
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<span style="font-size:14px;"> local stress (kbar)-103303.36 0.03 0.00</span>
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<span style="font-size:14px;"> 0.03-103303.33 0.00</span>
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<span style="font-size:14px;"> 0.00 0.00 89345.22</span>
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<span style="font-size:14px;"> nonloc. stress (kbar) 7795.83 -0.00 0.00</span>
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</blockquote>