title: Electronic structure and elastic properties of Y(n+1)Co(3n+5)B(2n) ([Formula: see text]).
abstract: We have studied the electronic structure and elastic properties of Y(n+1)Co(3n+5)B(2n) (space group P6/mmm), where n = 1, 2, 3 and [Formula: see text], using ab initio calculations. These ternary borides exhibit a bulk-modulus-to-C(44) ratio from 1.6 to 1.9, which is rather unusual for ceramics. This may be understood on the basis of the electronic structure: predominantly covalent-ionic YCo(3)B(2) layers are interleaved with predominantly metallic YCo(5) layers. Covalent-ionic bonding between B and Co may give rise to a large bulk modulus, while weak coupling between the YCo(3)B(2) and YCo(5) layers may be responsible for the low C(44) value. On the basis of the similarity in electronic structure and elasticity data, it is reasonable to assume that the Y(n+1)Co(3n+5)B(2n) compounds investigated here may exhibit similar properties to the so-called MAX phases (Barsoum 2000 Prog. Solid State Chem. 28 201).
authors.forename: Denis
authors.initials: D
authors.lastname: Music
authors.forename: Jochen M
authors.initials: JM
authors.lastname: Schneider