Hi Julie, The same happened to us for a metallic system. The cure seems the use of a quite dense k-point grid (like 3K - 4K for the single atom primitive cell) and to keep the M&K grid fixed across the different deformations.
Comments from the list appreciated. Regards, Roberto On Fri, 20 Feb 2009, Julie Smart wrote:
Hello all, I have a question about the changes of the total energy of a system under strain. I have relaxed the system I have first under "Variablecell False" by "MaxForceTol 0.04eV/Ang" and then I turned on the "Variablecell true" and decreased the "MaxForceTol " to 0.01 eV/Ang to have the lattice parameters optimized as well. When I change the lattice parameter in "z direction" to put the strain on the system sometimes the enrgy goes lower than the energy of the relaxed system!!! it may also happen when I insert the starin in further steps. I mean it first increases and then I see the decrease of the energy!!! This is occuring to me while I have tried the optimization of my system checking different "energyshifts" and setting this parameter to the one that makes the energy of my system go to the lowst! The basis and the pseudo also have been checked very carefully. Please let me know where I am going wrong. Regards, Julie
