Elastic properties and inter-atomic bonding in new superconductor KFe2Se2 from first principles calculations

TL;DR

This paper uses first-principles calculations to predict the elastic properties and analyze the inter-atomic bonding in the newly discovered superconductor KFe2Se2, revealing its mechanical stability, anisotropy, and bonding nature.

Contribution

First ab initio prediction of elastic properties and bonding characteristics of KFe2Se2, a new superconductor in the 122 family, providing insights into its mechanical behavior.

Findings

KFe2Se2 is relatively soft and mechanically stable.

The material exhibits significant elastic anisotropy.

Inter-atomic bonding includes ionic, covalent, and metallic contributions.

Abstract

Very recently (November, 2010, PRB, 82, 180520R) the first 122-like ternary superconductor KxFe2Se2 with enhanced TC ~ 31K has been discovered. This finding has stimulated much activity in search of related materials and triggered the intense studies of their properties. Indeed already in 2010-2011 the superconductivity (TC ~ 27-33K) was also found in the series of new synthesized 122 phases such as CsxFe2Se2, RbxFe2Se2, (TlK)xFeySe2 etc. which have formed today the new family of superconducting iron-based materials without toxic As. Here, using the ab initio FLAPW-GGA method we have predicted for the first time the elastic properties for KFe2Se2 and discussed their interplay with inter-atomic bonding for this system. Our data reveal that the examined phase is relatively soft material. In addition, this system is mechanically stable, adopts considerable elastic anisotropy, and demonstrates brittleness. These conclusions agree with the bonding picture for KFe2Se2, where the inter-atomic bonding is highly anisotropic and includes ionic, covalent and metallic contributions.