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--></style></head><body lang="EN-US"><div class="WordSection1"><p class="MsoNormal">Dear QE Users,</p><p class="MsoNormal"><o:p> </o:p></p><p class="MsoNormal">Greetings,</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. </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(attached), 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? </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.</p><p class="MsoNormal">Chunhua </p><p class="MsoNormal"><o:p> </o:p></p><p class="MsoNormal"> The input can be seen below:</p><p class="MsoNormal"><o:p> </o:p></p><p class="MsoNormal">&CONTROL</p><p class="MsoNormal"> calculation = "vc-relax"</p><p class="MsoNormal"> forc_conv_thr = 1.00000e-06</p><p class="MsoNormal"> etot_conv_thr = 1.00000e-04</p><p class="MsoNormal"> max_seconds = 28800</p><p class="MsoNormal"> outdir='./outdir'</p><p class="MsoNormal"> pseudo_dir = "/home/chunhua/QuantumEspresso/PAW_precision_pseudos"</p><p class="MsoNormal"> restart_mode = "from_scratch"</p><p class="MsoNormal"> nstep=100</p><p class="MsoNormal">/</p><p class="MsoNormal"><o:p> </o:p></p><p class="MsoNormal">&SYSTEM</p><p class="MsoNormal"> degauss = 1.00000e-02</p><p class="MsoNormal"> ecutrho = 5.00000e+02</p><p class="MsoNormal"> ecutwfc = 1.00000e+02</p><p class="MsoNormal"> ibrav = 0</p><p class="MsoNormal"> nat = 217</p><p class="MsoNormal"> ntyp = 4</p><p class="MsoNormal"> occupations = "smearing"</p><p class="MsoNormal"> smearing = "gaussian"</p><p class="MsoNormal">/</p><p class="MsoNormal"><o:p> </o:p></p><p class="MsoNormal">&ELECTRONS</p><p class="MsoNormal"> conv_thr = 1.00000e-04</p><p class="MsoNormal"> electron_maxstep = 200</p><p class="MsoNormal"> mixing_beta = 1.00000e-01</p><p class="MsoNormal"> startingpot = "atomic"</p><p class="MsoNormal"> startingwfc = "atomic+random"</p><p class="MsoNormal">/</p><p class="MsoNormal"><o:p> </o:p></p><p class="MsoNormal">&IONS</p><p class="MsoNormal"> ion_dynamics = "bfgs"</p><p class="MsoNormal">/</p><p class="MsoNormal"><o:p> </o:p></p><p class="MsoNormal">&CELL</p><p class="MsoNormal"> cell_dofree = "all"</p><p class="MsoNormal"> cell_dynamics = "bfgs"</p><p class="MsoNormal"> press_conv_thr = 5.00000e-01</p><p class="MsoNormal">/</p><p class="MsoNormal"><o:p> </o:p></p><p class="MsoNormal">K_POINTS {gamma}</p><p class="MsoNormal"><o:p> </o:p></p><p class="MsoNormal">CELL_PARAMETERS {angstrom}</p><p class="MsoNormal"> 32.039000 0.000000 0.000000</p><p class="MsoNormal"> 0.000000 30.039000 0.000000</p><p class="MsoNormal"> 0.000000 0.000000 50.039000</p><p class="MsoNormal"><o:p> </o:p></p><p class="MsoNormal">ATOMIC_SPECIES</p><p class="MsoNormal">O 15.99940 O.pbe-n-kjpaw_psl.1.0.0.UPF</p><p class="MsoNormal">N 14.00674 N.pbe-n-kjpaw_psl.1.0.0.UPF</p><p class="MsoNormal">H 1.00794 H.pbe-kjpaw_psl.1.0.0.UPF</p><p class="MsoNormal">C 12.01070 C.pbe-n-kjpaw_psl.1.0.0.UPF</p><p class="MsoNormal"><o:p> </o:p></p><p class="MsoNormal"><o:p> </o:p></p><p class="MsoNormal">ATOMIC_POSITIONS {angstrom}</p><p class="MsoNormal">N 7.659071 9.660491 38.488224</p><p class="MsoNormal">H 7.708071 8.734491 38.052224</p><p class="MsoNormal">C 6.804071 9.663491 39.674224</p><p class="MsoNormal">H 6.853071 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5.708071 7.920491 36.811224</p><p class="MsoNormal">H 6.083071 8.063491 35.099224</p><p class="MsoNormal">C 4.001071 8.140491 35.553224</p><p class="MsoNormal">H 3.524071 7.632491 34.716224</p><p class="MsoNormal">H 3.394071 7.973491 36.445224</p><p class="MsoNormal">C 4.088071 9.648491 35.257224</p><p class="MsoNormal">H 3.082071 10.070491 35.304224</p><p class="MsoNormal">H 4.690071 10.124491 36.032224</p><p class="MsoNormal">N 4.631071 9.918491 33.908224</p><p class="MsoNormal">H 4.492071 9.204491 33.200224</p><p class="MsoNormal">C 5.273071 11.030491 33.510224</p><p class="MsoNormal">N 5.762071 11.890491 34.403224</p><p class="MsoNormal">H 6.110071 11.454491 35.261224</p><p class="MsoNormal">H 6.192071 12.760491 34.139224</p><p class="MsoNormal">N 5.422071 11.259491 32.203224</p><p class="MsoNormal">H 5.245071 10.476491 31.572224</p><p class="MsoNormal">H 5.846071 12.094491 31.830224</p><p class="MsoNormal">N 5.110071 5.999491 33.312224</p><p class="MsoNormal">H 4.132071 6.031491 33.549224</p><p class="MsoNormal">C 5.520071 6.282491 31.949224</p><p class="MsoNormal">H 6.218071 5.530491 31.578224</p><p class="MsoNormal">H 4.642071 6.304491 31.304224</p><p class="MsoNormal">C 6.180071 7.662491 31.974224</p><p class="MsoNormal">O 5.557071 8.653491 31.577224</p><p class="MsoNormal">N 7.401071 7.755491 32.505224</p><p class="MsoNormal">H 7.804071 6.910491 32.897224</p><p class="MsoNormal">C 8.196071 8.975491 32.522224</p><p class="MsoNormal">H 7.555071 9.791491 32.834224</p><p class="MsoNormal">C 8.669071 9.260491 31.085224</p><p class="MsoNormal">O 8.578071 8.380491 30.229224</p><p class="MsoNormal">C 9.344071 8.853491 33.543224</p><p class="MsoNormal">H 9.373071 7.852491 33.979224</p><p class="MsoNormal">H 10.297071 9.005491 33.035224</p><p class="MsoNormal">C 9.234071 9.874491 34.693224</p><p class="MsoNormal">H 10.177071 9.857491 35.240224</p><p class="MsoNormal">H 9.079071 10.885491 34.326224</p><p class="MsoNormal">C 8.148071 9.550491 35.688224</p><p 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13.159491 14.561224</p><p class="MsoNormal">C 17.620071 14.438491 13.622224</p><p class="MsoNormal">O 18.729071 14.463491 14.161224</p><p class="MsoNormal">C 15.092071 14.890491 13.889224</p><p class="MsoNormal">H 14.335071 14.959491 14.669224</p><p class="MsoNormal">H 15.317071 15.895491 13.531224</p><p class="MsoNormal">C 14.483071 14.072491 12.759224</p><p class="MsoNormal">O 14.898071 14.310491 11.605224</p><p class="MsoNormal">O 13.617071 13.227491 13.064224</p><p class="MsoNormal">N 17.502071 14.628491 12.311224</p><p class="MsoNormal">H 16.573071 14.587491 11.898224</p><p class="MsoNormal">C 18.631071 14.909491 11.442224</p><p class="MsoNormal">H 19.459071 14.234491 11.658224</p><p class="MsoNormal">H 18.317071 14.753491 10.409224</p><p class="MsoNormal">C 19.084071 16.357491 11.615224</p><p class="MsoNormal">O 18.870071 17.178491 10.724224</p><p class="MsoNormal">N 19.702071 16.676491 12.757224</p><p class="MsoNormal">H 19.801071 15.946491 13.453224</p><p class="MsoNormal">C 20.225071 18.006491 13.046224</p><p class="MsoNormal">H 19.349071 18.643491 13.141224</p><p class="MsoNormal">C 21.133071 18.452491 11.879224</p><p class="MsoNormal">O 22.136071 17.791491 11.600224</p><p class="MsoNormal">C 20.921071 18.000491 14.419224</p><p class="MsoNormal">H 20.340071 17.388491 15.111224</p><p class="MsoNormal">H 21.922071 17.572491 14.346224</p><p class="MsoNormal">C 21.008071 19.404491 15.041224</p><p class="MsoNormal">H 21.744071 20.002491 14.504224</p><p class="MsoNormal">H 20.038071 19.895491 14.979224</p><p class="MsoNormal">C 21.398071 19.367491 16.516224</p><p class="MsoNormal">O 21.993071 18.350491 16.933224</p><p class="MsoNormal">O 21.073071 20.356491 17.206224</p><p class="MsoNormal">N 20.779071 19.524491 11.149224</p><p class="MsoNormal">C 21.322071 19.773491 9.823224</p><p class="MsoNormal">H 21.423071 18.836491 9.271224</p><p class="MsoNormal">C 22.694071 20.449491 9.879224</p><p class="MsoNormal">O 22.811071 21.649491 9.631224</p><p 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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>