Electronic Structure of ZnCNi3

TL;DR

This study investigates the electronic structure of ZnCNi3, revealing similarities to MgCNi3 but lacking superconductivity, which may be due to carbon deficiency affecting its physical properties.

Contribution

It provides a detailed electronic structure comparison between ZnCNi3 and MgCNi3, proposing that C deficiency explains the absence of superconductivity and related discrepancies.

Findings

Electronic structures are similar, especially the van Hove singularity.

Lack of superconductivity may be due to C deficiency.

Discrepancies in lattice constants and specific heat are explained by C deficiency.

Abstract

According to a recent report by Park et al, ZnCNi3 is isostructural and isovalent to the superconducting (Tc = 8 K) anti-perovskite, MgCNi3, but shows no indication of a superconducting transition down to 2K. A comparison of calculated electronic structures shows that the main features of MgCNi3, particularly the van Hove singularity near the Fermi energy, are preserved in ZnCNi3. Thus the reported lack of superconductivity in ZnCNi3 is not explainable in terms of Tc being driven to a very low value by a small Fermi level density of states. We propose that the lack of superconductivity, the small value of the linear specific heat coefficient, gamma, and the discrepancy between theoretical and experimental lattice constants can all be explained if the material is assumed to be a C-deficient alpha-ZnCNi3 similar to the analogous non-superconducting phase of MgCNi3.