Direct calculation of electron density in density-functional theory

A new approach for the study of ground states of many-electron systems is developed via direct calculation of the density in density-functional theory. Not using the Kohn-Sham equations, the method divides a system into subsystems in physical space and determines the density for each subsystem. The method is demonstrated with calculations for the nitrogen molecule, which is divided into two atomic subsystems. We expect this approach to enable calcultions for large molecules beyond the reach of conventional methods.