Electronic and magnetic properties of MX3 ( M=Th, U and X=Ga, Ge, Si, Al) compounds

Full text: I have investigated the electronic and magnetic properties of MX3 compounds in the framework of density functional theory within the generalized gradient approximation. An all-electron linear augmented plane wave method is used. Both the energy band calculation and the total density of states curves of these compounds indicate that spin-orbit interaction has a considerable effect and can not be ignored. Thus the electronic and magnetic calculation has been performed in the presence of spin-orbit coupling. The total energy MX3 compounds as a function of volume is calculated. The calculations have been performed with some volume around the one corresponding to the experimental lattice parameter. Minimizing the E-V curve, we have then found the equilibrium lattice parameter, bulk modulus and its pressure derivative which show good agreement with experimental. The density of states calculation indicates that there is a pseudo gap between f-f bonding-ant bonding bands. The Fermi energy, Ef, is located near the center of the pseudo gap. It is also clear from the partial DOS of X and M atoms that the dominant states near the Ef are Th 6d and U 5f electrons. Furthermore by using the calculated density of state at the Fermi level I obtained the linear coefficient of electronic specific heat. This shows that the value of for UX3 is larger than the corresponding value obtained for ThX3. It is clear that the larger value of for UX3 compounds is due to the existence of a U 5f peak near the Fermi energy. We have also calculated the electric field gradient, which may be regarded as a measure of the asymmetry in charge distribution, at X site in MX3 compounds. (authors)