【開催予告】2026.10.22 -第202回構材ゼミ- Dr. Jean-Marc Joubert (Institut de Chimie et des Matériaux Paris-Est, CNRS-UPEC)
- 日時
-
2026年10月22日（木曜日）15:30-16:30
- 場所
-
NIMS千現地区 先進構造材料研究棟5階カンファレンスルーム
- 講演題目
-
Crystal chemistry and phase stability of the A15 structure
- 講演者
-
Dr.Jean-Marc Joubert
Institut de Chimie et des Matériaux Paris-Est, CNRS-UPEC, Thiais, France
Jean-marc.joubert@cnrs.fr
Abstract:
This presentation reviews the structural properties of the A15 phase, a topologically close-packed (TCP) structure stable in 61 binary systems, with a focus on its homogeneity domain, the structural accommodation of composition via site occupancy analysis, and its thermodynamic stability. The discussion combines a careful review of the available literature data and our original experimental data in the following binary systems: Al–Nb, Al–V, Nb–Sn, Os–V, Pt–V, Re–V, Sn–V, and Sn–Zr, and systematic DFT calculations in all the V-based systems. Notably, we demonstrate that the unexpected position of the A15 phase in the Os–V and Re–V phase diagrams does not result from vanadium occupying the sites of lower coordination. Instead, it arises from a large deviation from the ideal V3Os and V3Re compounds by atomic substitution. This is shown by the experimental analysis of site occupancies, DFT calculations, and thermodynamic description of the systems. Consequently, the coordination preference is always governed by electronic rather than geometric criteria: elements with lower valence consistently favor the higher-coordination site (14) over the lower coordination site (12). This behavior contrasts with that of the other TCP phases (σ and Laves) for which a comparison is provided.