Crystal structure of the Th₂Ni₁₀Al₁₅ phase solved using electron diffraction tomography

Due course of study of the Th-Ni-Al system, new Th₂Ni₁₀Al₁₅ phase was revealed. Despite the prolonged heat treatment- the studied alloy did not attained equilibrium and contained many intermetallic phases along with the phase of an interest. Thus, structure solution of this phase was performed by only viable option - electron crystallography, specifically electron diffraction tomography. Such structures (containing actinides, transition metals and Al) were never solved before using this method. Since it is possible that Th, as heavy scatterer, will smear the Fourier map, making it hard to find the positions of the Al atoms - case study was performed prior structure solution of the Th₂Ni₁₀Al₁₅ phase. Finally, it was determined that the Th₂Ni₁₀Al₁₅ structure has an orthorhombic unit cell with following lattice parameters a = 3.99 Å, b = 11.18 Å, c = 17.34 Å and Immm (No.71) space group. Its structural model contains 54 atoms in the unit cell, distributed over 10 unique atom positions. This structure can be described both as stacking of coordination polyhedra formed around heavy atoms and as layered structure with unique architecture.