Structural stability and structural imitation of La2Co17-xMx (M = Mn, Mo, Nb, Ti, V, Al, Cr, Ni and Si)

The structural stability of La2Co17- xMx ( M = Mn, Mo, Nb, Ti, V, Al, Cr, Ni and Si) based on the interatomic potential has been studied. The calculated site preference of the third element M is found to be the 6c site, which is in agreement with the experiments. In the calculations, if the crystal cohesive energy of La2Co16Mn is taken as the highest one in the crystallization of La2Co17- xMx, the lowest content x of the third element M ( M = Mn, Mo, Nb, Ti and V) required to stabilize La2Co17- xMx, is near that found in the experiments. The differences of the cell parameters between the calculated and the experimental values are less than 0.4%. The differences of the atomic parameters for Co ( or M) between the calculated and the experimental values are about or even smaller than 1%, and that of La is about 3%. Because the energies of La( Co1-xAlx)(13) are lower than those of La-2(Co1-xAlx)(17), La-2(Co1- xAlx)(17) could not be formed in the experiments. In the calculations, with either a range of deformation of the structure or the reconstruction of the initial structure La2Co17 from LaCo5, the same results including the cohesive energy curves and the crystallographic parameters can be retrieved after the action of the interatomic potentials.