S Jalali Asadabadi - Department of Physics, Faculty of Science, University of Isfahan, Hezar Gerib Avenue
A. R. Faghihi
M. R Sotodeh

Where accurate ab initio calculations are difficult to perform, our understanding of the physical properties is often based on a model Hamiltonian approach. An important parameter in such models is the effective coulomb interaction U between the localized electrons in the system. In particular this interaction is very important in the strongly correlated systems. In resent decade, it has become very popular to calculate these parameters using the ab initio density functional (DF) formalism in the local density (LD) approximation [1]. According to this theory we used the method introduced by Gunnarsson and Anisimov [2], and we have considered the effective coulomb electron-electron interaction in the MnO crystal. In this work, we have investigated the effect of nanoscale on the on-site Coulomb repulsion Hubbard parameter U in the MnO nanocrystal. The Nanoscale effect is also compared with the magnetic ordering effect