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--></style></head><body lang="EN-US"><div class="WordSection1"><p class="MsoNormal">Dear QE Users,<o:p></o:p></p><p class="MsoNormal"><o:p> </o:p></p><p class="MsoNormal">Greetings,<o:p></o:p></p><p class="MsoNormal"><o:p> </o:p></p><p class="MsoNormal">I have been studying QE for half a year, currently I am working on optimizing the crystal structure of gelatin molecule. The initial coordinates was obtained from a protein ‘.pdb’ file of gelatin. I do not know whether it is the best configuration so that I use QE to run the vc-relax. <o:p></o:p></p><p class="MsoNormal"><o:p> </o:p></p><p class="MsoNormal">The problem I have come across is that the ‘forc_conv_thr’ is hard to be achieved, when I plot the history of force, I can see after a certain number of iterations, the total force would vibrate around a certain value(~1e-2) a little bit. Theoretically the total force should be decreasing to 0, I have tried to adjust the input parameters, like ecutwfc(50~150), mixing_beta(0.1 ~ 0.7), bfgs to damp, but not effective. Please give any suggestions on what should I do? <o:p></o:p></p><p class="MsoNormal"><o:p> </o:p></p><p class="MsoNormal"><o:p> </o:p></p><p class="MsoNormal">Thanks a lot and Best regards.<o:p></o:p></p><p class="MsoNormal">Chunhua <o:p></o:p></p><p class="MsoNormal"><o:p> </o:p></p><p class="MsoNormal">The input can be seen below:<o:p></o:p></p><p class="MsoNormal"><o:p> </o:p></p><p class="MsoNormal">&CONTROL<o:p></o:p></p><p class="MsoNormal"> calculation = "vc-relax"<o:p></o:p></p><p class="MsoNormal"> forc_conv_thr = 1.00000e-06<o:p></o:p></p><p class="MsoNormal"> etot_conv_thr = 1.00000e-04<o:p></o:p></p><p class="MsoNormal"> max_seconds = 28800<o:p></o:p></p><p class="MsoNormal"> outdir='./outdir'<o:p></o:p></p><p class="MsoNormal"> pseudo_dir = "/home/chunhua/QuantumEspresso/PAW_precision_pseudos"<o:p></o:p></p><p class="MsoNormal"> restart_mode = "from_scratch"<o:p></o:p></p><p class="MsoNormal"> nstep=100<o:p></o:p></p><p class="MsoNormal">/<o:p></o:p></p><p class="MsoNormal"><o:p> </o:p></p><p class="MsoNormal">&SYSTEM<o:p></o:p></p><p class="MsoNormal"> degauss = 1.00000e-02<o:p></o:p></p><p class="MsoNormal"> ecutrho = 5.00000e+02<o:p></o:p></p><p class="MsoNormal"> ecutwfc = 1.00000e+02<o:p></o:p></p><p class="MsoNormal"> ibrav = 0<o:p></o:p></p><p class="MsoNormal"> nat = 217<o:p></o:p></p><p class="MsoNormal"> ntyp = 4<o:p></o:p></p><p class="MsoNormal"> occupations = "smearing"<o:p></o:p></p><p class="MsoNormal"> smearing = "gaussian"<o:p></o:p></p><p class="MsoNormal">/<o:p></o:p></p><p class="MsoNormal"><o:p> </o:p></p><p class="MsoNormal">&ELECTRONS<o:p></o:p></p><p class="MsoNormal"> conv_thr = 1.00000e-04<o:p></o:p></p><p class="MsoNormal"> electron_maxstep = 200<o:p></o:p></p><p class="MsoNormal"> mixing_beta = 1.00000e-01<o:p></o:p></p><p class="MsoNormal"> startingpot = "atomic"<o:p></o:p></p><p class="MsoNormal"> startingwfc = "atomic+random"<o:p></o:p></p><p class="MsoNormal">/<o:p></o:p></p><p class="MsoNormal"><o:p> </o:p></p><p class="MsoNormal">&IONS<o:p></o:p></p><p class="MsoNormal"> ion_dynamics = "bfgs"<o:p></o:p></p><p class="MsoNormal">/<o:p></o:p></p><p class="MsoNormal"><o:p> </o:p></p><p class="MsoNormal">&CELL<o:p></o:p></p><p class="MsoNormal"> cell_dofree = "all"<o:p></o:p></p><p class="MsoNormal"> cell_dynamics = "bfgs"<o:p></o:p></p><p class="MsoNormal"> press_conv_thr = 5.00000e-01<o:p></o:p></p><p class="MsoNormal">/<o:p></o:p></p><p class="MsoNormal"><o:p> </o:p></p><p class="MsoNormal">K_POINTS {gamma}<o:p></o:p></p><p class="MsoNormal"><o:p> </o:p></p><p class="MsoNormal">CELL_PARAMETERS {angstrom}<o:p></o:p></p><p class="MsoNormal">32.039000 0.000000 0.000000<o:p></o:p></p><p class="MsoNormal"> 0.000000 30.039000 0.000000<o:p></o:p></p><p class="MsoNormal"> 0.000000 0.000000 50.039000<o:p></o:p></p><p class="MsoNormal"><o:p> </o:p></p><p class="MsoNormal">ATOMIC_SPECIES<o:p></o:p></p><p class="MsoNormal">O 15.99940 O.pbe-n-kjpaw_psl.1.0.0.UPF<o:p></o:p></p><p class="MsoNormal">N 14.00674 N.pbe-n-kjpaw_psl.1.0.0.UPF<o:p></o:p></p><p class="MsoNormal">H 1.00794 H.pbe-kjpaw_psl.1.0.0.UPF<o:p></o:p></p><p class="MsoNormal">C 12.01070 C.pbe-n-kjpaw_psl.1.0.0.UPF<o:p></o:p></p><p class="MsoNormal"><o:p> </o:p></p><p class="MsoNormal"><o:p> </o:p></p><p class="MsoNormal">ATOMIC_POSITIONS {angstrom}<o:p></o:p></p><p class="MsoNormal">N 7.659071 9.660491 38.488224<o:p></o:p></p><p class="MsoNormal">H 7.708071 8.734491 38.052224<o:p></o:p></p><p class="MsoNormal">C 6.804071 9.663491 39.674224<o:p></o:p></p><p class="MsoNormal">H 6.853071 10.650491 40.137224<o:p></o:p></p><p class="MsoNormal">C 7.465071 8.662491 40.595224<o:p></o:p></p><p class="MsoNormal">O 8.658071 8.812491 40.838224<o:p></o:p></p><p class="MsoNormal">C 5.336071 9.344491 39.352224<o:p></o:p></p><p class="MsoNormal">H 4.737071 9.431491 40.259224<o:p></o:p></p><p class="MsoNormal">……………………….</p><p class="MsoNormal">……………………….</p><p class="MsoNormal"><o:p> </o:p></p><p style="margin:0in;margin-bottom:.0001pt;background:white;vertical-align:baseline"><span style="color:black">-----------------------------------------------------------</span></p><p style="margin:0in;margin-bottom:.0001pt;background:white;vertical-align:baseline"><b><span style="font-size:10.0pt;font-family:"Times New Roman",serif;color:#4472C4;border:none windowtext 1.0pt;padding:0in;mso-fareast-language:ZH-CN">Chunhua Ying</span></b><span style="font-size:10.0pt;font-family:"Times New Roman",serif;color:black;border:none windowtext 1.0pt;padding:0in;mso-fareast-language:ZH-CN"><br>Ph.D. Student</span><span style="color:black;mso-fareast-language:ZH-CN"><o:p></o:p></span></p><p style="margin:0in;margin-bottom:.0001pt;background:white;vertical-align:baseline"><span style="font-size:10.0pt;font-family:"Times New Roman",serif;color:black;border:none windowtext 1.0pt;padding:0in;mso-fareast-language:ZH-CN">School of Mechanical and Materials Engineering</span><span style="color:black;mso-fareast-language:ZH-CN"><o:p></o:p></span></p><p style="margin:0in;margin-bottom:.0001pt;background:white;vertical-align:baseline"><b><span style="font-size:10.0pt;font-family:inherit;color:black;border:none windowtext 1.0pt;padding:0in;mso-fareast-language:ZH-CN">Washington State University </span></b><b><span style="color:black;mso-fareast-language:ZH-CN"><o:p></o:p></span></b></p><p style="margin:0in;margin-bottom:.0001pt;background:white;vertical-align:baseline"><span style="font-size:10.0pt;font-family:"Times New Roman",serif;color:black;border:none windowtext 1.0pt;padding:0in;background:white;mso-fareast-language:ZH-CN">Engineering Laboratory Building, 105</span><span style="color:black;mso-fareast-language:ZH-CN"><o:p></o:p></span></p><p style="margin:0in;margin-bottom:.0001pt;background:white;vertical-align:baseline"><span style="font-size:10.0pt;font-family:"Times New Roman",serif;color:black;border:none windowtext 1.0pt;padding:0in;background:white;mso-fareast-language:ZH-CN">900 NE College Ave, </span><span style="font-size:10.0pt;font-family:"Times New Roman",serif;color:black;border:none windowtext 1.0pt;padding:0in;mso-fareast-language:ZH-CN">Pullman, WA 99164</span><span style="color:black;mso-fareast-language:ZH-CN"><o:p></o:p></span></p><p class="MsoNormal"><o:p> </o:p></p></div></body></html>