Single crystal X-ray structure investigation and electronic structure studies of La-deficient nickel stannide La_4.87Ni₁₂Sn₂₄ grown from Sn flux

The cubic La_4.87Ni₁₂Sn₂₄ was synthesized in reactions involving liquid Sn. The compound crystallizes in the cubic syngony, space group Im3̄, Z = 2, cell parameter a = 11.9662(14) Å, and is related to the Gd₃Ni₈Sn₁₆ structure type previously refined from powder X-ray data. The crystal structure of La_4.87Ni₁₂Sn₂₄ was solved and refined using single crystal X-ray data to final R₁ = 2.67%, wR₂ = 6.92%. The refinement showed no mixed occupancy with Sn for the La(1) site, contrary to what was proposed for Gd₃Ni₈Sn₁₆. Instead, a partial occupancy of 87% was detected for the La(1) at 2a. Electronic structure calculations show that the system is metallic, and the density of states at the Fermi level falls at a peak with the highest contribution coming from La(1) atoms, if the compound with ideal occupancies La₅Ni₁₂Sn₂₄ is assumed. The deficiency of the La(1) site could therefore originate in the lowering of the total energy of the system due to the loss of 0.39 electrons per formula unit. Magnetic measurement data indicates nearly temperature independent Pauli paramagnetism. Theoretical estimation of the magnetic susceptibility after including core diamagnetic corrections agrees well with experiment.