Dear Anna, The usual preliminary work that you should do before going into production runs is to try to reproduce some experimental/previously published theoretical results using the pseudopotentials you are interested in and trying to see which one does better. The data you could reproduce includes (but is definitely not limited to) bulk moduli, lattice constants, band structures, phonon mode frequencies, properties of compounds etc. For bare Ti, you might be hard-pressed to find data so perhaps something like TiO or TiO2 properties would make your life easier.
Best, Hande -- Hande Toffoli Department of Physics Office 439 Middle East Technical University Ankara 06531, Turkey Tel : +90 312 210 3264 http://www.physics.metu.edu.tr/~hande