Abstract:
Very recently, as an important step in the development of layered
Fe-free pnictide-oxide superconductors, the new phase
BaTi$_2$Bi$_2$O was discovered which has the
highest $T_C$ (${\sim}\,4.6\,$K)
among all related non-doped systems. In this Letter, we report
for the first time the electronic bands,
Fermi surface topology, total and partial
densities of electronic states for BaTi$_2$Bi$_2$O
obtained by means of the first-principles
FLAPW-GGA calculations. The inter-atomic bonding picture is described as a
high-anisotropic mixture of metallic,
covalent, and ionic contributions. Besides, the
structural and electronic factors, which can be responsible for the increased
transition temperature for BaTi$_2$Bi$_2$O (as compared
with related pnictide-oxides
BaTi$_2$As$_2$O and BaTi$_2$Sb$_2$O), are discussed.
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