Dear Forum, I have some questions on setting the parameter set (ecfixed,q2sigma,qcurtz) in cp.x of espresso-4.2.1. I use SiO2 of example18 in source code.
I found that when I adjust (ecfixed,q2sigma,qcurtz) the average volume at equilibrium state varies. How do think of this volume disagreement? What is the criteria to select the best (ecfixed,q2sigma,qcurtz) value? I summarized my results in detail following. In this code, the original value is (ecfixed=16,q2sigma=2,qcutz=150). I did adjustment with all other parameter fixed as the same to check the pressure, volume, and total energy at equilibrium state of 10Kbar-10K. I adjust ecfixed first, then q2sigma, then qcutz. 1. adjusting ecfixed. ecfixed (with q2sigma=2,qcutz=150) average volume volume vibarion 17.1 1340 small 17.0 1350 small 16.9 1360 small 16.8 1370 small 16 1330 larger 19 1390 larger All above have similar pressure vibration. The larger ecfixed, the lower total energy. How do think of this volume discrepancy? Is this satisfying with inaccuracy? What is the criteria to select the best ecfixed value? Now, without anyother base, personally, I think that ecfixed=16.8 has small volume vibration and it has the largest volume among those with small volume vibration. Maybe ecfixed=16.8 it is. 2. adjust q2sigma q2sigma (with ecfixed=16.8,qcutz=150) volume volume vibration 1.6 1420 larger 1.8 1345 larger 2.0 1370 small 2.2 1380 larger 2.4 1370 larger 2.6 1330 larger All above have similar pressure vibration. The smaller q2sigma, the lower total energy. I think that q2sigma=2 is the best because it has smallest volume vibration. Right? 3. adjusting qcutz qcutz (with ecfixed=16.8,q2sigma=2) volume volume vibration 50 1310 small 80 1335 small 120 1360 small 150 1370 small 180 1380 small 400 1370 small All above have similar pressure vibration. The smaller qcutz, the lower total energy. They have similar results except the volume discrepancy. So what is the criteria to select ? In sum, regarding the volume discrepancy, how to select the best value for (ecfixed,q2sigma,qcurtz) ? Thanks for you attention. Any comment is grateful. WANG Riping 2010.1.7 -- ****************************************************************************** WANG Riping Ph.D student, Institute for Study of the Earth's Interior,Okayama University, 827 Yamada, Misasa, Tottori-ken 682-0193, Japan Tel: +81-858-43-3739(Office), 1215(Inst) E-mail: wang.riping.81 at gmail.com ****************************************************************************** -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20110107/9b746908/attachment.htm