  The structural, electronic and the bonding properties of the Sn-BEA are
investigated by using the periodic density functional theory. Each of the 9
different T-sites in the BEA were substituted by the Sn atom and all the 9
geometries were completely optimized using the plane wave basis set in
conjunction with the ultra-soft pseudopotential. On the basis of the structural
and the electronic properties, it has been demonstrated that the substitution
of the Sn atom in the BEA framework is an endothermic process and hence the
incorporation of the Sn in the BEA is limited. The lowest unoccupied molecular
orbitals (LUMO) energies have been used to characterize the Lewis acidity of
each T-site. On the basis of the relative cohesive energy and the LUMO energy,
T2 site is shown to be the most favorable site for the substitution of Sn atom
in the BEA framework.
