Hello I'm a newby in calculations with Quantum espresso and I think I'm trying to do an impossible task.
I want to do a structural optimization to a cell with 338 atoms (C, H, N and O) and approximate dimensions of 15*15*15 angstroms. If I choose Ecut of 18 Ry and a kpoint mesh of 1*1*1, with pz-rrkjus pseudopotential the optimisation takes 13 hours. With a 2*2*2 kpoint mesh is taking more than 4 days, and hasn't finished yet. I believe that for reliable results I need a larger Ecut (at least 30 Ry, I suppose) and a number of kpoints in the order of thousands, which would imply in a calculation of several years. The cell is a P1 triclinic cell but about 300 atoms are fixed, because I only need to do particial optimisation. So, what can I do to have reliable results in useful time, or Quantum Espresso is not suitable for my task? Jos? Fernandes Departamento de Quimica Universidade de Aveiro 3810-193 Aveiro Portugal Tel: +351234370720 Fax: +351234370084
