The projector-augmented plane wave method applied to molecular bonding

The projector-augmented wave (PAW) method proposed by Blochl is an all-elec tron ab initio approach to electronic structure calculations. Using a local basis set expansion, the LSDA wave function is mapped onto a smooth image which can be treated with a plane wave basis set. of a practical size. We d iscuss our implementation of this approach and its application to the calcu lation of the bending properties of several second row and transition metal diatomic molecules. Comparisons are made between PAW and other methods. Ou r results for binding energy, bond length, and vibration frequency indicate that the accuracy of the PAW method is similar to that of local basis and finite grid methods. The convergence with respect to number of plane waves is sufficient that practical calculations are possible even for systems whi ch would be difficult to treat with pseudopotential methods. For example, f or the F-2 and Fe-2 dimers the bonding energy is converged with a 60 Ry cut off in the plane wave expansion. The local basis contributions that appear in the theory can be precomputed, and therefore, the overhead typically ass ociated with the local basis method is greatly reduced. For a fixed size of the plane wave basis set the execution times of the PAW method are similar to those of plane wave pseudopotential methods.