By draw, I think you mean visualization. Ovito or AtomEye should do the trick. They are free software used by research scientists. You can find them through google.
Two free (but good) software I've used before are Visual Molecular Dynamics (VMD) and Vesta. They contain several other useful features for basic simulations, and are very useful for preparing and checking input files for ab initio materials calculations using VASP, CASTEP and Quantum Espresso.