ABSTRACT
Due to the continuous increase in computer power as well as the tedious efforts invested in method development, electronic structure calculations are now becoming possible for larger and larger systems, expanding the application territory to systems that were previously exclusively treated by the classical force field methods. The ab initio molecular orbital calculations of a hundred atoms are routinely performed at the level of Hartree-Fock (HF) theory and density functional theory (DFT) with moderate basis sets. Although large-scale DFT calculations of several thousands of atoms have been reported,1 it seems difficult to go beyond that size, because the computational time and resources scale steeply with the system size N; the scaling is O(N3) for HF and DFT, and it is even higher for correlated wavefunction theories.
