Abstract
Recently, fragment molecular orbital (FMO) method has attracted much attention as an electronic state calculation method for macromolecular system. When the size of a molecule grows, the ratio of the dimer calculation in the total computing time grows in the FMO method (O(N3)). To overcome this difficulty, the dimer-es approximation was developed; the dimer SCF calculation between distant monomers was approximated by that for fragments with electrostatic interaction. It has a dramatic effect on the reduction of computing time without loss of the accuracy of calculation when the molecular size grows (O(N2)). However, it becomes one of the bottlenecks for a large molecule because it is necessary to calculate the coulomb integral at four centers in the dimer-es approximation. Then, for the speed-up of the coulomb integral, continuous multiple method (CMM) was implemented in FMO program ABINIT-MPX, and the accuracy of calculation and the computing time were investigated in this article.
