Phonon anomalies predict superconducting Tc for AlB2-type structures. Issue 38 (8th September 2015)

• Record Type: Journal Article
• Authors: Alarco, Jose A.; Talbot, Peter C.; Mackinnon, Ian D. R.
• Is Part Of: Physical chemistry chemical physics. Volume 17:Issue 38(2015)
• Page Start: 25090
• Page End: 25099
• Publication Date: 2015-09-08
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/c5cp04402b
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : The phonon anomaly, δ, calculated by ab initio DFT methods, indicates presence of superconductivity in Mg0.5 Ba0.5 B2 and other AlB2 -type structures. Abstract : We show that the well-known Kohn anomaly predicts T c for ordered AlB2 -type structures. We use ab initio density functional theory to calculate phonon dispersions for Mg1− x Al x B2 compositions and identify a phonon anomaly with magnitude that predicts experimental values of T c for all x . Key features of these anomalies correlate with the electronic structure of Mg1− x Al x B2 . This approach predicts T c for other known AlB2 -type structures as well as new compositions. We predict that Mg0.5 Ba0.5 B2 will show T c = 63.6 ± 6.6 K. Other forms of the Mg1− x Ba x B2 series will also be superconductors when successfully synthesised. Our calculations predict that the end-member composition, BaB2, is likely to show a T c significantly higher than currently achieved by other diborides although an applied pressure ∼16 GPa may be required to stabilise the structure.