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Manuscript Title: A projector augmented wave (PAW) code for electronic structure calculations, part I: atompaw for generating atom-centered functions.
Authors: N.A.W. Holzwarth, A.R. Tackett, G.E. Matthews
Program title: genproj
Catalogue identifier: ADNQ_v1_0
Distribution format: tar.gz
Journal reference: Comput. Phys. Commun. 135(2001)329
Programming language: Fortran.
Computer: DEC Alpha, IBM SP2.
Operating system: Unix.
RAM: 20M words
Keywords: Solid state physics, Band structure, Electronic structure calculations, Density functional calculation, Local density approximation, Projector augmented wave method, PAW, Calculational methods.
Classification: 7.3.

Nature of problem:
The projector augmented wave (PAW) method, developed by Blochl, is a very powerful tool for performing electronic structure calculations within density functional theory, combining some of the best features of pseudopotential and all-electron approaches. Developing a procedure for constructing the projector and basis functions for a PAW calculation is similar to the challenge of constructing of pseudopotentials for a pseudopotential calculation. The construction scheme used in the present scheme is very similar to the one originally suggested by Blochl and has now been demonstrated to work well for a number of complex materials.

Solution method:
The method starts with a self-consistent all-electron atomic structure calculation within the framework of density functional theory. The projector and basis functions are derived from the eigenstates of the all-electron atomic Hamiltonian. They are determined by iteratively solving radial differential equations.

Restrictions:
All atoms in the periodic table can be treated with this approach, although those with high atomic numbers will have systematic errors due to the neglect of relativistic effects in this version of the code. The local density approximation (LDA) is coded for the exchange-correlation functional in this version of the code; other functionals, such as the generalized gradient approximation could easily be added.
Also, in this version of the code, it is assumed that electron density due to frozen core electrons is contained within the augmentation sphere. This assumption obviates the need for pseudo core wave functions or core tail density functions. The accuracy of this assumption can be controlled by including upper core states within the PAW basis set.

Unusual features:
Some scripts are included to make it easy to generate plots of the output results using the Unix package gnuplot.

Running time:
10 minutes or less.