NUMERICAL GRIDS FOR DENSITY-FUNCTIONAL CALCULATIONS OF MOLECULAR-PROPERTIES

There is an increasing number of applications using methods based on d ensity functional theory (DFT) describing a large variety of systems o f chemical interest. All these calculations are performed through eval uations of integrals of exchange and correlation contributions to the energy and the potential, which depend on the density and also on its first and second derivatives (nonlocal functionals). Within our DF pro gram, the integrand is decomposed into single-center components, throu gh the introduction of weight functions, and its radial and angular de pendence can be chosen. In this article, we give a brief description o f these features, with compared performances of different grids for th e evaluation of different integrals, such as the total number of elect rons and the exchange and correlation energies. More complex propertie s, such as total energies and equilibrium geometries, are also studied with respect to the choice of the grid of points, in order to determi ne the most favorable radial and angular quadrature schemes. The incid ence of this choice is analyzed in the case of the metal-metal bond of the Ru2, Rh2, and Pd2 dimers. Finally, the use of an extended grid of points is shown necessary for systems involving weak interactions, su ch as the Ar2 molecule. (C) 1994 John Wiley & Sons, Inc.