  This work reports on the elastic and electronic properties of the newly
discovered superconductor Th2NiC2 (A .Machado, et al., Supercond. Sci. Technol.
25 (2012) 045010) as obtained within ab initio calculations. We found that
Th2NiC2 is mechanically stable and it will behave as a ductile material
exhibiting enhanced elastic anisotropy in shear and a rather low hardness Our
data reveal that for Th2NiC2 the Fermi level is located in a deep DOS minimum
and the experimentally observed increase in TC in the sequence Th2NiC2 ->
Th1.8Sc0.2NiC2 may be explained by the growth of N(EF). We also speculate that
(i) an increase in the hole concentration will promote exchange splitting of Ni
3d bands, therefore the hole-doped Th2NiC2 should have a certain concentration
border, where a phase transition from the superconducting to the magnetic state
will be expected, and (ii) an increase in N(EF) (and, probably, in TC) for
Th2NiC2-based materials may be also achieved by an alternative way: by electron
doping - for example, by partial substitution of V for Th or Cu for Ni, as well
as by partial substitution of N for C with the formation of Th-Ni carbonitrides
like Th2NiC2-xNx.
