Hi! I'd like to use quantum espresso in research of properties of MoS2 nanoparticles, modified with Co and Ni. This basically means calculations with 20 to 60 atoms of modified MoS2 slab and 10 to 30 atoms of interacting molecule, as well as 1- and 3-dimensional periodic calculations with same number of atoms. The atomic species of interest are: Mo, S, Co, Ni, H, C, N, O, K, Na, Li.
Before performing real calculations I'd like to reproduce geometry of several basic with reasonable agreement with expreimental data. The problem is choise of PP/functional pair. For some time I was stick with b3lyp and pbe functionals of gaussian-03 package with full-electron non-periodic calculations, wich resulted in good agreement with experimental data. However, I cannot find PPs for this functionals for QE and full-electron approach is a little too much for my new systems. With quick research I was able to generate simple PP for H atom, but got 0.78 A H-H bond length instead of 0.74, and runned into incompatibility of ultrasoft PP and Gamma algorithm. So, I decided to stop and search for advise. The questions are: 1. Can someone point a good review about PP approximation (both math and use)? 2. As well as planewave approach for basis sets (It is completly new for me, I used only GTO basis sets before) ? 3. And possibly a good library of PP (espetially interested in desription of generation procedure) ? 4. What the hell are K-points, given in K_points sections and how should I choose them for ultrasoft PP ? 5. Are geometry and energy errors in QE/DFT systematic, i.e. can I use some corrections coefficient or I should work with them as random values? Of course, I'm going at least to try to find and read reference articles for QE, yet my math skills are not very hight. -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20111208/31689c2b/attachment.htm