Equilibrium magnetic structure of NpSn$_3$

Actinide based compounds show very intersting physical properties due to the singular behaviour of their 5f electrons. The variation of these properties yields information on the electronic structure of the solid. We have focused on the NpSn$_{3 }$which exhibits antiferomagnetic phase at zero pressure. In this work to investigate the magnetic properties of NpSn$_{3}$, the total energy per primitive unit cell as a function of its volume in antiferomagnetic, feromagnetic and nonmagnetic phases are calculated using density functional theory within GGA and LDA approaches. We have found an antiferomagnetic ground state for NpSn$_{3}$ in both approches. We have also found that for unit cell valumes smaller than a certain value, the magnetic moment is quenched and therfore the two antiferomagnetic and nonmagnetic curves coincide. For larger volumes a net magnetic moment appears and the antiferomagnetic curve branches off the nonmagnetic one. The branching valoumes found in different approaches are different.