Hello, I have recently started to use siesta with a view to doing orderN calculations. So far all the calculations I have tried have become unstable in the first or second steps regardless of whether I manually tune the value of eta, set it to the value from a previous diagonalised calculation or use the chemical potential method (NB I would not expect the band gap to be small for these systems and the fermi level is about -3.7 eV). So I have a few questions which I have not been able to find answers for to see if I am doing something daft or impossible (Apologies if I've missed something obvious - I haven't studied DFT methods in great detail and I'm clutching at straws to find a way to optimise a particular set of crystal structures using DFT).
i) I'm using the GGA potentials that were converted from AbInit - are these compatible with the orderN method ? ii) The system is expected to contract quite a lot as it is a crystal structure with the solvent removed - is it a really bad idea to try an relax such a system using the orderN method ? iii) The gradients in output file always seem to be very large compared to those I've seen in presentations (even though the number of electrons is not too bad at the end of the first cycle) - does this indicate from the outset that the method is unlikely to work with a particular structure ? Thank you for any help or suggestions, Jeremy
