hi ,uesers here : i relax one crystal lattice vs energy: i have compute several energy list :
c E(RY) 2.795 -137.79266 2.78 -137.79248 2.77 -137.79233 2.8 -137.7927 2.81 -137.79275 2.82 -137.79275 2.83 -137.79278 2.84 -137.79276 2.85 -137.79279 2.86 -137.79272 2.87 -137.79265 2.88 -137.79258 2.9 -137.79229 2.95 -137.79122 these energy points are smooth and can be plotted parabola. the system has 12 atoms.the energy is different most at the third digit after radix point. so i think the average energy/atom is less 0.0001. i want to ask the within the precision of energy(my thinking is based on that :my above calculation is set ecutwfc:29, ecutrho:200,and the criterion is 35,350, the convergence is 0.0049345 ry.) so this small difference of energy can skip,i.e we can choose 2.77 which is regarded as the best structure? as why i ask this question,for the the structure of 2.85 has two big negative frequencies near -100cm-1, even if i add asr . but 2.77 has no negative frequency after i add asr. -- Xu Yuehua physics Department of Nanjing university China -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20071212/942e2fee/attachment.htm
