Spatial structure and stability of MonSim nanoparticles

By means of the ab initio DMol3 method MonSim nanoparticles and fragments of Mo3Si and MoSi2 crystal lattices are theoretically modeled. For both crystals a few neutral Mo4Si6 and Mo6Si6 fragments of different shapes and symmetry are considered. In each case, after cluster separation its geometry is optimized, as a result of which the geometric structure noticeably changes and its stability increases. In order to theoretically search for the spatial configurations of Mo4Si6 and Mo6Si6 nanoparticle, two approaches are used: 1) in the most stable Fe4C6 and Fe6C6 isomers found previously, iron and carbon atoms are replaced by molybdenum and silicon respectively and then the geometry is optimized to obtain new equilibrium distances and angles; 2) the search for main Mo4Si6 and Mo6Si6 configurations is performed using the binominal scheme, starting from Mo2, MoSi, and Si2 dimers. The nanoparticle structures are found to contain metal atom chains and isolated pairs and triples of silicon atoms. In most cases, the nanoparticle stability proves to be higher than that of the crystal clusters.