The crystal structure of Ni₁₃Sn₈P₃ elucidated from HREM

The crystal structure of Ni₁₃Sn₈P₃ was elucidated from High Resolution Electron Microscopy Images. It was tound to be a superstructure of the B8-type (NiAs-type) structure with Sn and P atoms ordered at the hexagonally closepacked array and Ni atoms in all octahedral and in two out of every eleven trigonal bipyramidal sites. The structure motif within a NiSn B8-type matrix comprises triangles of P atoms with two of the three edges capped by Ni atoms in trigonal bipyramidal sites. This motif is repeated along the [01̄1]_B8 zone axis so that the structure can be envisaged as pairs of face-sharing Ni centered Edshammar polyhedra corner-connected along [01̄1]_B8. The reciprocal lattice (H) can be described as H = G + mq₁ + nq₂ (where G refers to the Bragg reflections of the underlying B8-type structure, q₁ = 1/11 [112̄1]_B8, q₂ = 1/22 [6̄515]_B8 and m and n are integers. The resultant triclinic (P1̄) unit cell parameters are a = 6.456 Å, b = 21.291 Å, c = 13.247 Å, α = 81.052°, β = 56.260° and γ = 68.221°.