Starting from Slater's explanation of the Hund's rule, in these 80 years origin of magnetism has been believed to be the exchange interaction between electrons in atoms, molecules, and bulk materials. His theory assumes degenerate states for kinetic and potential energies. Starting from Davidson on the excited states in He atom in 1965, several papers have been published to doubt the Slater's theory. However, unfortunately these contributions used simple HF theory and not so accurate. We have continuously made a series of accurate calculations including electron interactions fully to finalize this contradiction, since this is a very important problem to understand the origin of magnetism. To confirm our results we numerically check the virial theorem for equilibrium states; 2T+V=3P&Omega=0. This theorem requires for the total energy E=T+V to be E=V/2=-T; T and V are not independent. Based on this fundamental theorem, we have completely certified that the Slater's perturbation theory violates this necessary condition, and is wrong. The origin of magnetism is not the exchange interaction, but it is mainly the interaction between positively charged nucleus and electrons with spin. Last year we extended this new finding up to the second Hund's rule, which is for the angular momentum states, as the first theoretical contribution to understand it. In my talk detailed theory and numerical results will be given, and model calculations assuming perturbation theories are categorized to be good or wrong. |