A CONJUGATE-GRADIENT TECHNIQUE IN A CAR PARRINELLO-TYPE PROGRAM

Using a non-local norm-conserving pseudopotential, we developed an all -bands preconditioned conjugate gradient method by improving the preco nditioner that can be applied to all-bands. As a result, our conjugate gradient method provides rapid convergence in the energy minimization , especially in large-scale electronic structure calculations. We eluc idated the importance of the preconditioning in the conjugate gradient method. In the numerical calculation for a simple Si crystal, the eff iciency of our preconditioned conjugate method was demonstrated and co mpared with the steepest descent, the preconditioned steepest descent and the usual conjugate gradient methods.