Efficient density-functional theory integrations by locally augmented radial grids.

Standard density-functional theory integration grids have proven insufficient for the meta generalized gradient approximation description of weakly bound complexes [E. R. Johnson et al., Chem. Phys. Lett. 394, 334 (2004)]. This is caused by an insufficient radial resolution in the valence region of frequently used standard grids. We present an algorithm for the construction of locally augmented radial grids, which allows us to enhance the resolution of a given radial grid in a specified region, thus increasing the accuracy of the standard grid in a cost-efficient way. Test calculations with the Van Voorhis-Scuseria exchange and correlation functional for the Ar dimer confirm that a suitably constructed, locally augmented radial grid with 100 points provides an accuracy competitive to that of a 250-point nonaugmented grid. Time savings and possible applications for locally augmented radial grids are discussed.