Superbox method for order-N electronic structure calculations for very large systems

We have developed a superbox method for ab initio electronic structure calculations for very large systems. The method is applicable to density-fucntional or Hartree-Fock-based calculations. In this approach a molecule, a cluster, or a large supercell of a crystal is divided into a number of boxes. Self-consistent calculations are then carried out in parallel for each box, treating it either as a supercell or as a free unit. The wave function or the Green's function of the total system is then constructed by connecting the solutions obtained in the individual boxes by a rigorous and formally exact procedure that yields a self- consistent solution for the entire system. The method has been implemented by using the recently introduced Lagrange-function basis [1]. Examples will be presented using density functional theory to demonstrate the linear scaling of the approach with respect to the number of atoms in the system. [1] K. Varga, Z. Zhang, and S. T. Pantelides, Phys. Rev. Lett. 93, 176403 (2004).