Ab initio study of the elastic and electronic properties of tetragonal Th2NiC2

TL;DR

This study uses ab initio calculations to analyze the elastic and electronic properties of the superconductor Th2NiC2, revealing its stability, ductility, and potential ways to enhance its superconducting transition temperature.

Contribution

First ab initio investigation of Th2NiC2's elastic and electronic properties, linking electronic structure to superconductivity and proposing doping strategies for T_C enhancement.

Findings

Th2NiC2 is mechanically stable and ductile.

Fermi level is in a deep DOS minimum, influencing T_C.

Doping strategies may increase T_C or induce phase transitions.

Abstract

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.